Manchester United are 15 games into the Ruben Amorim era and their long-term crisis is worsening.

Sunday's 3-1 defeat to Brighton & Hove Albion at Old Trafford saw the United head coach channel his inner Ralf Rangnick and describe his team as possibly the worst in the club's 147-year history.

United had just suffered a fourth defeat in their last six Premier League matches and a fourth reverse in their last five Old Trafford outings. Such terrible form has left them sitting 13th in the table, 10 points above the relegation zone and 12 shy of the Champions League places.

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Mathematically, either Champions League qualification or relegation is still possible. In reality, the expectation is that United's season, based on their current form, will fizzle out and end in a mid-table finish.

Amorim arrived in Manchester in November tasked with trying to kick-start United's season. However, a complete transformation in style of play always meant that it carried its fair share of risks, particularly when the club's hierarchy had spent a small fortune during the summer recruiting players for a different style and system under Erik ten Hag.

Amorim acknowledged early on in his tenure that United would have to "suffer" as they adapted to his methods. He made the same admission again after Sunday's defeat to Brighton.

It is no secret that United's squad needs gutting and rebuilding this summer. Countless players need moving on and replacing with figures suitable for Amorim's 3-4-2-1 formation.

Nevertheless, regardless of how much time Amorim needs to build his ideal team to work hand-in-hand with his blueprint, United must improve - and fast. However, that collective craving will not be possible until United sort out their defensive problems.

Following the loss to Brighton, which marked a sixth Premier League home defeat of the season, United have now recorded just one clean sheet in 15 matches since Amorim took over. Only Everton have failed to breach United's new-look three-man defence.

Regardless of the teething issues Amorim is experiencing in his quest to successfully implement his new-look system and formation, keeping one clean sheet in 15 games for a club of United's stature is not good enough. United have conceded far too many goals throughout the campaign, sieving 31 since Amorim came in alone.

Furthermore, far too many of those goals have been conceded either via a set-piece or an avoidable individual mistake, highlighted by Andre Onana's blunder for Brighton's third at the weekend. The other two goals were also incredibly cheap to concede from a United point of view.

Not only did Yankuba Minteh's fifth-minute opener at Old Trafford quash any hopes United had of recording just a second clean sheet since Amorim's appointment, but it also marked the 10th time in the Portuguese chief's opening 15 matches that United had conceded the first goal.

United have been guilty far too often of giving themselves a mountain to climb in the quest for points. They are regularly having to chase games, resulting in them having to use more energy and alter Amorim's original approach.

Of course, when United have battled back to earn results, such as they did against Manchester City and Liverpool, they have earned praise for digging in deep and refusing to roll over. However, they have conceded first in two thirds of the games Amorim has been in charge of, and that is not sustainable in their search for success.

United have conceded far too many cheap goals in recent matches and that is something Amorim is so far failing to address. However, as a caveat, it must be documented that the players have to take their portion of the blame.

But with United continuing to give themselves a mountain to climb, often within the opening exchanges of matches, it is a problem Amorim and his players must address, as it is a massive problem that is yet to be fixed.