Full-time: Middlesbrough 1-3 Manchester United
Manchester United rise above Everton and Arsenal to fifth and extend their unbeaten Premier League run to 18 matches with a Sunday lunchtime victory at the Riverside Stadium
Marouane Fellaini heads home Ashley Young's excellent left-wing cross at the back post to put the visitors in front after half an hour
Jesse Lingard doubles the lead with a second-half screamer from distance
Substitute Rudy Gestede reduces the deficit from close range after Chris Smalling's botched clearance
Antonio Valencia wraps up all three points in stoppage time after an unfortunate slip from former United goalkeeper Victor Valdes
Lingard limps off with an injury ahead of England's double-header against Germany and Lithuania
Caretaker boss Steve Agnew takes charge of Middlesbrough for the first time following Thursday's dismissal of Aitor Karanka
Despite ending a run of 509 minutes without a league goal, relegation battlers 'Boro, now winless in 11 top-flight matches, remain 19th and five points adrift of safety
An irate Mourinho stated that he believed his side would 'probably lose' due to fatigue caused by a relentless fixture list
That just about does it for our live coverage of Middlesbrough vs Manchester United, thanks for following along.
Tottenham vs Southampton is up next, but our attention now switches to the small matter of a heavyweight clash between Manchester City and Liverpool at the Etihad Stadium.
I hope you can join me for that one.
Just in case Mourinho had led you to believe that it was all doom and gloom for United at the moment...
It seems that things have kicked off big time in the tunnel. Not sure what caused the trouble, but I'm sure we will hear more about it soon.
Most popular: Tony Pulis expects Arsene Wenger to stay at Arsenal
It's worth noting that Mourinho made his triumphant exit after that third goal went in. You wonder if that spat between Bailly and Gestede carried on after the final whistle.
Middlesbrough 1-3 Manchester United
Oh, Victor Valdes.
The Spaniard's slip while trying to clear a routine backpass allows Valencia to nip in and tap home into an empty net.
Goal: Middlesbrough 1-3 Manchester United (Antonio Valencia)
A break in play now after a real disagreement between Bailly and Gestede sparks something of a melee involving both sets of players.
A chance for Middlesbrough but Negredo is unable to make proper contact with a Gestede flick-on under pressure from Smalling.
Middlesbrough appeal in vain for a penalty after a battling Negredo works his way past Smalling and is held up by a timely sliding challenge from Jones.
Six across the back for Mourinho as United try to preserve their lead late on. Gestede's limited movement is making things difficult for Middlesbrough up front.
A quite incredible stat that bears repeating...
Lingard seems to have picked up and injury and limps off to be replaced by Martial.
Gestede, who has not been moving at all freely, receives further strapping to his hamstring.
Can Middlesbrough find an equaliser?
Middlesbrough's eight-and-a-half hour stretch without a league goal finally comes to an end.
Gestede, who had been clutching that noticeably sore hamstring, nutmegs De Gea from close range after De Roon beats Bailly to the header following a hooked clearance from Jones that soars high into the air.
Smalling completely botched an attempted clearance with his wrong foot and that allowed Gestede the chance to net his first league goal since a January move from Aston Villa.
Goal: Middlesbrough 1-2 Manchester United (Rudy Gestede)
Middlesbrough push forward in search of a goal that would set up a grandstand finish. Traore makes inroads down that right flank and a mishit cross from Barragan is claimed by De Gea.
Rojo then makes an important clearance and another ball towards Gestede is beyond the Benin international's reach.
Mourinho responds to that double change by withdrawing Mata in favour of another centre-back in Rojo.
The Argentine defender, despite wolfing down that banana, looked dead on his feet during the final moments against Rostov and Mourinho stated before kick-off that it would be difficult for him to play today.
Let's see how he gets on.
With his team looking embarrassingly bereft of pace, Agnew sends on the fast but wildly unpredictable Adama Traore in place Leadbitter.
Ramirez also makes way for Gestede, who will join Negredo in a front two.
Middlesbrough finally discover that actually putting crosses into the box with a striker of Negredo's ilk could prove an effective tactic. It's taken them long enough.
Jones just does enough to ensure that the the former Manchester City man heads a deep Ramirez delivery wide.
Better from Middlesbrough as Negredo heads straight at De Gea after a pinpoint cross from Downing.
It's not long before Lingard is speeding forward once again. Middlesbrough look like Wile E. Coyote in pursuit.
Bailly wins the ball deep inside United's half and passes to Lingard, who races forward on the counter-attack.
With Middlesbrough's slow defence inexplicably content to keep backing off and give him an ocean of space in which to operate, the England midfielder fires an unstoppable 25-yard shot past Valdes and into the top corner.
That was a real screamer. Game over?
Goal: Middlesbrough 0-2 Manchester United (Jesse Lingard)
Middlesbrough are still largely dominating possession but, as you might expect from a team that have now not scored a league goal for over eight hours, are completely and utterly toothless.
Rashford with a poor shot that flies high and wide.
At the other end, Leadbitter dwells too long in possession and misses a great chance to play in Negredo. Frustrating.
The pace of Lingard and Rashford continues to cause problems for Middlesbrough.
The game begins to take on a more open feel before a long ball towards Ramirez gets held up in the wind. The Uruguayan eventually fouls Young and any momentum is lost.
Fabio's left-wing cross is just too high for Negredo and Young is forced to turn it behind for a corner that is eventually claimed confidently by De Gea.
Some lazy tracking from Ramirez leads to De Roon wiping out Lingard. Barragan steps in to intercept his low cross towards Rashford.
Strong defending from Gibson to stay with the elusive Rashford and deflect a cross back off the striker and out for a goal kick.
An early 'Boro corner is cleared and Fabio is lucky not to be cautioned for a high tackle on Valencia.
The second half is off and running.
Smalling does his best Jones impression by trying to complete a header back to De Gea and completely missing the ball.
He won't want to see that again.
Much for the caretaker boss and assistant Jordan to ponder at the break. Middlesbrough enjoyed plenty of possession in that first half but need to do much more with it.
United do not look entirely comfortable playing three at the back. That uncertainty can be exploited.
Agnew will be bitterly disappointed with the goal. Barragan was too easily deceived by Young and Fellaini was the only blue shirt in the box when he guided that header in at the back post.
His aerial threat is obviously well-established, but Gibson, Fabio and Valdes could all have done much better.
Fellaini's 30th-minute header is all that separates the two teams at the interval after a bright opening period.
United started the afternoon firmly on the back foot but steadily turned the screw and would probably have scored earlier had they been able to deploy a more authoritative figure in the box and were it not for Valdes denying Rashford (twice) and Valencia.
Middlesbrough began sharply and responded well to going behind, playing some nifty football but, as per usual, not really looking that likely to score from open play. Ramirez came closest with a curling shot that was beaten away by De Gea.
They aren't out of it yet, however.
Middlesbrough 0-1 Manchester United
Rashford has Middlesbrough's defence back-pedalling towards their own goal. Mata makes a clever run to his left, but an attempted backheel is cut out by Bernardo.
One minute of added time will be played at the end of this first half.
Bailly concedes another corner. Smalling heads clear and wins a free-kick following a not-so-subtle shove from Gibson.
After being picked out by Lingard, Rashford again beats Bernardo for pace. Valdes intervenes to prevent his low pass from reaching Mata.
That particular battle will be of real concern to Agnew. It's a complete mismatch in terms of speed.
A heart-in-mouth moment for Fellaini as United's goalscorer almost puts a Ramirez cross through his own net.
'Boro have responded well since the goal. Fabio, Leadbitter and Ramirez combine to good effect and a slip from Jones almost sees Negredo latch onto a cutback from De Roon.
'Boro look to respond quickly and Negredo heads wide after what looked like a clear push on Jones.
Adam Clayton then foolishly prevents Carrick from taking a quick free-kick and duly has his name taken. Pointless.
Middlesbrough made an undeniably positive start to this game, but United have been well on top for the last 15 minutes or so and now that pressure tells.
Young, not properly checked by Barragan, whips in a cracking back-post cross from the left and the oft-maligned Fellaini ghosts in behind Gibson and Fabio to head home.
Negligent defending from the hosts.
Goal: Middlesbrough 0-1 Manchester United (Marouane Fellaini)
A questionable advantage played by Moss after a foul on Rashford leaves United with no attackers in the box and their latest attack breaks down.
A low ball from Lingard flashes across the six-yard box before going safe.
Jones clashes with Negredo and picks up the game's first yellow card.
What a superb double stop.
Valdes denies Rashford from close range after a fine cross from Mata before scrambling to keep out Valencia's rebound effort from a tight angle.
That's three top saves from Valdes already this afternoon.
Middlesbrough clear the corner as Smalling goes down after some grappling with Bernardo. He appeals hopefully for a penalty that was never likely to be given.
Downing bizarrely misses the ball and allows Rashford to head back towards that left byline.
His latest cutback towards Lingard is cleared behind by an alert Ramirez.
Fellaini rises above Ben Gibson to head wide after Rashford wins a corner off Antonio Barragan while trying to set-up Lingard in the six-yard box.
A meaty but fair challenge from Leadbitter on Lingard draws a rapturous round of applause. 'Boro look up for this.
75% possession for Middlesbrough during this opening 15 minutes. Aside from Rashford's early chance, Agnew will be pleased with what he has seen from his side thus far.
Ramirez, teed up nicely by Fabio, steps inside Bailly and unleashes a curling effort that is beaten away by De Gea.
The Uruguayan's subsequent corner is poor and fails to pick out a red shirt.
Leadbitter tries his luck with an ambitious long-range shot that was always rising.
Former Red Devil Fabio then just overhits a pass down the channel intended for Ramirez. Middlesbrough have played some good football during the early stages of this match.
As quick as a flash, Rashford bursts clear beyond a sluggish Bernardo. One-on-one with Valdes, his low shot is well saved.
That should have been the opener.
Bailly stays down after a bit of a kick from Ramirez that is somehow missed by the referee.
He will be fine to continue.
'Boro are loading plenty of crosses into the box early on.
After Ramirez overhits his initial effort from the left, Downing, whose training ground row with Karanka was said to have been the final straw that led to the manager's exit, floats a dangerous ball in towards Marten de Roon that is deflected over by a crucial touch from Smalling.
A short corner from Ramirez and Grant Leadbitter is deflected out for a throw-in and United survive.
Referee Jon Moss blows his whistle and Agnew's second caretaker spell in charge of Middlesbrough is underway.
He's been accused on social media of sticking to a very Karanka-esque lineup, so it will be interesting to see if he has been able to implement any changes at all during his short time in charge to date.
United, unbeaten in their last 17 league games, go into today's contest seventh following Everton's rout of 10-man Hull at Goodison Park yesterday.
They can leapfrog both the Toffees and Arsenal into fifth with a win at the Riverside, although an inferior goal difference means that a point would see them remain where they are.
A downcast Mourinho confirms to BT Sport that, while Rojo and Mkhitaryan are on the bench, it will be very difficult for either of them to play today.
The self-proclaimed 'Special One' also insists that his players are not only suffering from physical fatigue.
For those of you who may have missed Mourinho's post-Rostov rant, in which he declared that his team would 'probably lose' today, here is another reminder...
While no exact time frame has been put on Agnew's caretaker tenure, Gibson sounds hopeful that the 51-year-old - who has already enlisted the help of experienced former Harry Redknapp assistant Joe Jordan - will remain at the club for many years to come.
A positive result today against a weary United team would be a fantastic way to kick off what is essentially an 11-game job interview.
No pressure, Steve.
Speaking to The Times this week, 'Boro's Steve Gibson, widely considered among the most patient and forgiving chairmen in English football, insisted that Karanka had not been sacked but rather sacrificed himself.
I've had a lot of discussions with Aitor since the weekend. We agreed that a different approach is required Aitor is tired, he has worked so hard for our football club over the last three and half years and the tension surrounding the end of last season would have taken its toll on anyone. Then we had a very busy summer.
He was working his socks off trying to bring players in and he hasn't really had a break since the minute he walked through the door. What we concluded - he and I - was that he perhaps wasn't the guy at this point in time to deliver that change.
I know people are cynical when you say that a decision was mutual, but he wasn't sacked. He sacrificed himself. He's in a good frame of mind. I think he's relieved. He has been enormous for our club. He has progressed us and he will have learned an enormous amount from this experience.
Only one of the Premier League's bottom five won yesterday, so Middlesbrough - who, including today, boast a couple of games in hand over the two teams directly above them - remain 19th and five points adrift of safety before kick-off.
Karanka's departure after three-and-a-half years at the helm and promotion from the Championship came amid a desperate run of 10 league matches without a win that stretches back to before Christmas.
'Boro are also the top-flight's lowest scorers with a pitiful 19 goals to their name so far this term. Even hapless and rock-bottom Sunderland have managed to net five more than that.
"I'd like to thank Middlesbrough for a wonderful opportunity and the players, staff and all the people at the club who I have worked with," Karanka said after his exit. "I'd also like to thank the fans for their support. This club will always hold a special place for me and I wish everyone connected with Middlesbrough Football Club the very best for the future."
Mourinho swaps seven from Thursday night as David De Gea, Phil Jones, Ashley Young, Michael Carrick, Marouane Fellaini, Jesse Lingard and Marcus Rashford all come in.
Eric Bailly, Chris Smalling, Antonio Valencia and Juan Mata are the only players to retain their starting berths. Sergio Romero, Rojo and Henrikh Mkhitaryan drop to the bench.
Still no Rooney for United, although Martial does feature as a substitute. Blind is out.
Agnew makes four changes to the last team last fielded by Karanka, with Brad Guzan making way for former United goalkeeper Victor Valdes.
Gaston Ramirez, Stewart Downing and Alvaro Negredo also come in, with Adama Traore and Cristhian Stuani named as substitutes. Bernardo keeps his place in the back four, while Gestede is deemed fit enough for the bench.
He takes a seat alongside the returning Guedioura. As expected, the hosts are without Friend, Chambers, Ayala and Bamford.
Official team news is imminent. Standby...
Confusion over Rooney's status for today's trip to Teeside was caused by Gareth Southgate, who, after omitting his captain from the England squad for an upcoming international double-header against Germany and Lithuania due to a combination of injury issues and a lack of regular first-team football, stated that the player had a chance of featuring.
However, Mourinho's pre-Rostov assessment of his condition did not sound overwhelmingly positive...
"Rooney is injured," he said. "He had some kick in his knee area, so he can't even come out to the pitch. He stays inside the medical department."
Rooney is believed to have sustained that blow during an accidental training ground collision with Phil Jones.
For United, Paul Pogba is sidelined as the result of a hamstring problem that saw him limp out of Thursday night's unconvincing Europa League last-16 second-leg victory against FC Rostov. Daley Blind is doubtful after being substituted in the same game following a blow to the head.
Those injuries, along with Marcos Rojo's late-game struggles that required a banana to fix, caused Mourinho to further lament the fatigue caused by a truly hectic fixture list.
Wayne Rooney, Anthony Martial and even Bastian Schweinsteiger could all return this afternoon, but Zlatan Ibrahimovic and Ander Herrera are both serving domestic suspensions.
Meanwhile, young striker James Wilson continues to recover from an anterior cruciate ligament injury suffered during a loan spell at Derby County in October.
January signing Adlene Guedioura is available once again for 'Boro after being cup-tied for last weekend's predictable 2-0 FA Cup quarter-final defeat to Manchester City, while powerful striker Rudy Gestede and Colombian centre-back Bernardo Espinosa could make their respective returns from injury.
However, defensive trio George Friend (calf), Calum Chambers (foot) and Daniel Ayala (hamstring) remain out.
Patrick Bamford has not trained all week due to illness and it would be a surprise to see him involved today.
Before we delve further into Middlesbrough's plight and examine Mourinho's latest transparent attempts to install a siege mentality at Old Trafford, let's quickly run through the latest injury lines before the official teamsheet arrives in around 20 minutes or so...
Good morning, rise and shine and welcome to IBTimes UK's live coverage of a Sunday lunchtime Premier League clash at the Riverside Stadium, where caretaker boss Steve Agnew takes charge of relegation battlers Middlesbrough for the very first time against Manchester United following Thursday's arguably overdue dismissal of former Jose Mourinho assistant Aitor Karanka.
We will have minute-by-minute updates for you after kick-off at midday. Injury news, confirmed lineups and pre-match thoughts from both managers to come before then.
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