Twenty-four hours earlier, Chelsea were the team with everything to prove when they took on Manchester City at Stamford Bridge.

Now - after a home defeat by Leeds - Manchester United and head coach Michael Carrick travel to the same venue on Saturday with major questions to answer as well.

It had been anticipated Carrick and his team would have a 10-point cushion and be cruising to a place in next season's Champions League.

Instead, they know defeat will cut their advantage to four, with a queue of clubs desperate to take advantage of any weakness.

A first home defeat in his 11-game tenure, one victory in four games, no clean sheet in five, a potential central defensive crisis and boos ringing in his ears at half-time.

This is uncharted territory for Carrick, who has seemed so unflappable since replacing Ruben Amorim in January.

Now the pressure is well and truly on.

Central defensive issues

Over the next 48 hours, Manchester United will find out whether Harry Maguire will receive an additional punishment for his red card at Bournemouth last month after he was charged with improper conduct by the Football Association (FA) for something he said to fourth official Matt Donohue as he made his way off the field.

An additional suspension would rule him out of the Chelsea game, which Matthijs de Ligt is almost certain to miss as he deals with a long-term back problem.

Martinez will also miss out - plus home games against Brentford and Liverpool - after he was dismissed for violent conduct for pulling Dominic Calvert-Lewin's hair in the second half.

Carrick has suggested United will appeal against the red card. Unless they are successful, his only available central defenders at Stamford Bridge will be 19-year-old Ayden Heaven and 20-year-old Leny Yoro, who found it difficult to deal with Calvert-Lewin.

"That's why we've got a squad," countered Carrick. "We have got players we can call upon. We'll go there and look forward to the game.

"Hopefully Licha [Martinez] is still available. I think certainly that he should be after that, but we'll see."

Red Devils' midfield weakness

It has already been established Manchester United will be trying to sign at least two central midfield players in the summer.

Casemiro's impending departure creates one space but the reality is there is no depth.

Kobbie Mainoo's absence with what Carrick said before the game was a "small issue" deprived Manchester United of an effective link between defence and attack, someone who can take the ball in tight spaces and move it on quickly.

It sounds simple, yet when it is not there, the loss is all too apparent.

Manuel Ugarte does not have Mainoo's control on the ball, or his awareness. The Uruguay midfielder was not Manchester United's worst player, but he lacks the ability to lift a toiling team.

He works hard and hopes someone else can create the magic. This is not enough for where United are, let alone where they want to be.

It will probably be Thursday, when Carrick is due to speak to the media again before the Chelsea trip, when an indication of Mainoo's availability for Chelsea and beyond will be clarified.

If the England international is missing again, it will be a major issue, even if Carrick tried to make light of it.

"He has been fine when he has played since I have been here," he said.

"This was a tough game, a tough night - not just for him. When we went down to 10 men I thought he was really important and did a lot of covering for other players."

Carrick also took the bold decision to leave Bryan Mbeumo on the bench for the first time in the Premier League this season. It did not work.

Neither Mbeumo nor Amad Diallo have found their form since returning from Africa Cup of Nations duty. Matheus Cunha flits in and out of games and Benjamin Sesko - who had the home side's best two chances and was unlucky not to find the net - has been more effective off the bench.

It means the burden falls on skipper Bruno Fernandes to create opportunities.

Fernandes claimed a 17th Premier League assist, three short of the record for a season, when he crossed for Casemiro to head home. But deep in stoppage time, when he had the chance to cross deep into the penalty area again, he only found a Leeds head. Someone has to share the responsibility.

Pressure on Carrick

As frustrating as it can be for the media, which benefited enormously from Amorim's rent-a-quote period in charge, his calmness and refusal to get flustered has been viewed as one of Carrick's major strengths.

Yet when results do not go well, it can look like inaction.

Should he have made changes earlier? Should he have selected different players to start with? Can he cope with the pressure?

These are all questions that are asked after defeats, even if nothing much has changed from victorious days.

Carrick's Manchester United have to be viewed over a period of time.

It was unfortunate for the head coach that minority owner Sir Jim Ratcliffe was in the directors' box to hear the half-time booing, to witness a tepid opening period, and the failed rescue attempt.

The loss will sting. But not as much as if it is repeated at Stamford Bridge - somewhere Manchester United traditionally struggle for victories, right back to the 1960s, and have won only twice since 2002.

If it is, it will be one win in five and the gap to Chelsea will be down to four points and Champions League qualification will no longer be viewed as certain.

Carrick was bullish as he assessed the situation. Deep down, there must be some concern as well.

"Whatever happened tonight is not going to suddenly change my opinion on what we are as a team," he said.

"It is a big end to the season. We have done a lot of good things so far and the mentality and the character and the boys wanting to do well - I have never doubted that." (BBC)