It feels like Manchester United are a few high quality signings away from being where they need to. Jose Mourinho says so himself, putting the players he already has down while praising Juventus' board for their transfer business - United's rivals spend big to stay on top, United are falling behind.

Mourinho teams are supposed to be compact, tough to break down and competitive - in the derby, City teased and pulled on a thread which unravelled a gulf in class.

Mourinho says Man Utd need a top level centre-back. Maybe two. And a midfielder or three. But is that really the case?

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United have the highest wage bill in the Premier League and a negative goal difference. So what do they actually need to sort out, and how could they do it in the January transfer window?

Centre-backs

Ideal examples

Sergio Ramos (Real Madrid), Raphael Varane (Real Madrid), Giorgio Chiellini (Juventus), Diego Godin (Atletico Madrid), Virgil Van Dijk (Liverpool), Toby Alderweireld (Spurs).

United need a commanding centre-back who is ready-made for Premier League action. Mourinho doesn't like to play kids and wants someone who is a leader, a player who can captain the side and one who is able to carry the weight of expectation that Mourinho places on their shoulders. He needs to be aggressive, strong and to have proved himself at an elite level. And it would really help if he was cheap.

A big problem is that the name 'Man Utd' adds about £30million on top of an already disproportionately priced player and of these defenders, three currently play for the biggest teams in Europe, one has just signed for title-chasing Liverpool and another would require negotiating with Daniel Levy.

Paying £100+million for a 32-year-old Diego Godin seems a little unrealistic, especially if you consider that this is real money used on the planet earth for someone to play a sport for a couple of years. But what price can you put on a clean sheet?

Would any of these players really want to leave their respective clubs to join a team on such unstable ground? Alderweireld makes the most sense and his contract is up next year - Spurs have the option to extend by a year but that would activate a £25m release clause. The ball would be in Alderweireld's court to demand huge wages, so United might need to scout the lower tier of available players.

Expensive not-perfect examples

Milan Skriniar (Inter), Samuel Umtiti (Barcelona), Kostas Manolas (Roma), Harry Maguire (Leicester), Mats Hummels (Bayern), Kalidou Koulibaly (Napoli)

Every single one of these would cost at least £70m to a Premier League club, with Maguire being touted at around £80m during peak transfer gossip season in the summer. Would Ed Woodward be willing to sanction a near-£100m for a player unproven in England? What if it turns out Koulibaly can't fix problems on his own? Do any of them fit the captain mentality that United really need?

Stefan De Vrij of Inter Milan is another possible target and at 26 years old should be about to enter his peak years... but he's not one of the world's very best defenders. Signing De Vrij would be like signing a clear talent with high potential from a European league for a lot of money. The exact kind of thing they did with Eric Bailly.

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Future world stars

Ruben Dias (Benfica), Matthijs De Ligt (Ajax), Niklas Sule (Bayern), Marquinhos (PSG)

De Ligt is almost certainly off to Barcelona in the summer but Ruben Dias hasn't yet been strongly linked with a move to one of Europe's biggest clubs. Still only 21, Dias has played for Portugal, having broken into the Benfica first team last season, and massive things are expected of him.

Under the right coaching, this strong, intelligent, well-positioned central defender could dominate penalty areas for years to come and Benfica's business model of selling their best talents before fully developed might suit the United budget. But is he ready? Can Mourinho afford another Victor Lindelof?

It'd take a huge price to take any of these to Old Trafford and it's unlikely a rising first team star like Sule or Marquinhos would leave Bayern Munich or PSG.

Potential stars/cheaper options

Jamaal Lascelles (Newcastle), James Tarkowski (Burnley), Scott McKenna (Aberdeen), Nathan Ake (Bournemouth), Kristoffer Ajer (Celtic)

Burnley's centre-backs don't let much past them and perhaps Tarkowski could prove to be the Gary Pallister player Mourinho seems so desperate to find.

Lascelles is surely destined for big things at 24 and is Newcastle captain, McKenna is built like a fridge-freezer, is only 22 and has already captained Scotland after a dramatic rise from obscurity.

Ake has been immense this season but Bournemouth might quite like the cash (and for this reason he's not a cheap option...), while Ajer is slowly turning into a capable Van Dijk replacement at Celtic, performing the kind of ball-playing centre-back role that Mourinho is after.

Midfielders

United's centre-backs aren't alone to blame for United's negative goal difference. The strikers aren't taking their chances and the midfield are making errors, turning the ball over in dangerous positions and simply not winning the ball back with any great urgency.

Mourinho's midfielders in his best teams tended to be in their mid-to-late 20s, must shoulder responsibility and be able to play in a counter-attacking team. Below are some potential suitors who suit those parameters and stand a chance of being prised away from their clubs.

Ideal examples

Ivan Rakitic (Barcelona), Koke (Atletico Madrid), Toni Kroos (Real Madrid), N'Golo Kante (Chelsea), Christian Eriksen (Spurs), Ruben Neves (Wolves), Idrissa Gueye (Everton)

"Mr Woodward, sir, your card has been declined."

The problem United have here is that if Fred is worth £52m, it is only fair that Idrissa Gueye should cost around £400m and that's just not something Woodward is likely to sanction. His approach to the transfer market has seen some big-name players come in to the club but they are footballers who help shift merchandise and increase social media following, making the more famous individuals more likely to be on a United-branded radar.

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While Kroos (who is still only 28) would be a massive coup, would he bring the energy and tenacity needed to provide snap in the middle of the park?

Expensive examples

Marco Veratti (PSG), Marcelo Brosovic (Inter Milan), Kevin Strootman (Roma), Abdoulaye Doucoure (Watford), Adrian Rabiot (PSG), Sebastian Rudy (Schalke), Eric Dier (Spurs)

If United really want a central midfielder to do what Nemanja Matic and Paul Pogba currently don't seem very good at doing - and are willing to go over their overdraft - there are brilliant players out there who might be lured with the offer of fourth place and a run at the cups.

Strootman only just signed for Marseille, while Veratti and Rabiot are trying to win the Champions League with PSG, but Dier, Doucoure and Rudy would be moving to a 'larger' club were they to sign for Man Utd. It would cost far more than could possibly be deemed sensible to sign any of them. Let Fred be a warning to us all.

Luxury wrong examples

Sergej Milinkovic-Savic (Lazio), Thiago Alcantara (Bayern Munich), Miralem Pjanic (Juventus), Sergi Roberto (Barcelona)

Tall, creative, box-to-box and full of tricks, Milinkovic-Savic might not be the kind of player United need while Pogba is on the payroll, while Thiago is exactly the kind of intricate, technical pass-and-mover that Mourinho would sub off in the 55th minute to have Marouane Fellaini replace as a battering ram.

Pjanic is similar to Thiago, while Roberto would very likely be shunted into a few different positions while Mourinho works out what he is. Then he'd be subbed off for Fellaini. All of these players would cost astonishing amounts of money.

Future world stars

Lucas Paqueta (Flamengo), Sergio Gomez (Borussia Dortmund), Gedson Fernandes (Benfica)

Man Utd should be able to attract the most shiny of football's golden boys and of the wonderkids currently making a name for themselves, Brazil's Paqueta stands out.

The lesson of Fred still unlearned, Paqueta's neat-and-tidy, bright playmaker style is vaguely similar to that of Juan Mata and most likely wouldn't play his best under Mourinho, a coach who likes to strip and chisel away creativity until the player resembles a cog for the (very effective) machine.

Gomez will get game time at Dortmund, Fernandes needs to develop at Benfica before being put into a reserve squad, and if history has taught us anything, it's that Mourinho wants his midfielders to be Champions League-ready upon purchase.

Cheaper options

Aaron Ramsey (Arsenal), Wilfried Ndidi (Leicester), Tomas Soucek (Slavia Prague), Pierre-Emile Hjojberg (Southampton), Gelson Fernandes (Frankfurt), Danny Drinkwater (Chelsea, still)

Ramsey's contract runs out in the summer. He bursts from box-to-box in quick counter-attacks, gets stuck in to challenges, acts like a leader and is generally just excellent - it's almost too obvious a signing, Clive.

Ndidi was excellent in the World Cup, should be below the £50m mark and has made 36 tackles in the Premier League this season - as compared to Matic's 13 and Pogba's 11 - while Hjojberg appears to be growing into the player Pep Guardiola suspected he could be while at Bayern Munich. An unfashionable rummage in the bargain bin might reveal the likes of Fernandes and Soucek to be the midfield terriers United need to protect that defence.

Mourinho has spent a lot of money already at United but the players still don't seem to suit the coach, just as he doesn't quite seem to be getting the most out of his players. Would another manager get more out of the current playing staff? Would a couple of centre-backs solve United's defensive problems in the way Van Dijk has solidified Liverpool's back line?

United's big problem is that whatever the solution, it's going to cost them.