Who was at fault for Manchester United's heavy defeat to Bournemouth on Sunday afternoon?

How did they concede from another set-piece? Why did Noussair Mazraoui make such a rash challenge to concede a penalty? Why was Kobbie Mainoo's pass for the third goal so casual?

United fans had more questions than answers as they made an early exit from Old Trafford. Unfortunately, that has become a familiar feeling for supporters who have attended games this season and United were unable to give their fans something to celebrate ahead of Christmas.

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It was collectively a poor performance and indicative of United's form that the most consistent performer in the dressing room, Mazraoui, made such a bad tackle for the penalty.

Bournemouth were leading 1-0 at half-time but United ended the first half with momentum and a bright start when play resumed could have produced a completely different outcome.

Mazraoui conceded a penalty in the 60th minute instead. The challenge was clumsy, it was a stonewall penalty and Bruno Fernandes still protested the decision with the referee.

Although Old Trafford was already flat and the quietest it had been for some time, Justin Kluivert converting from the spot seemed to kill any hope the game could be salvaged that was remaining on the terraces and Bournemouth's third goal made sure of that just moments later.

Mazraoui hadn't put a foot wrong in a United shirt until that penalty. There's something incredibly endearing about a player who is a 7/10 each week but Mazraoui received a 4/10.

It was a stupid tackle, which was due to a lapse of concentration. Mazraoui can be forgiven and he's probably entitled to a mistake given he's had such an excellent season, but it felt like an error from a player who is becoming tired and would benefit from a game on the bench.

Mazraoui has started in 15 from a possible 17 games in the Premier League, he has started in each of the six Europa League fixtures and has started in one of three Carabao Cup matches, although he made a substitute appearance in the two cup games that he wasn't in the starting XI.

The 27-year-old has also made substitute appearances in two Premier League games that he didn't start in, which means he's made an appearance in every United fixture in all competitions.

So, nobody could blame Mazraoui for feeling slightly tired. It's a huge compliment to his quality that he's been so heavily involved, but perhaps it's time to give him a rest, especially when it's become clear that playing with two natural full-backs in the wing-backs role isn't working.

Playing Amad as the right wing-back and Diogo Dalot on the left would be the logical choice against Wolves. It would give Mazraoui a much-needed rest and Dalot might be envious.

Dalot is another defender who has been overplayed this season and he could do with being rotated. Just last month, a source admitted that he was currently feeling the effects of a gruelling campaign but said he's the type of character to continue to give everything for the team.

Mazraoui might be at the front of the queue for a deserved rest, though.