The Reds saw their lengthy unbeaten run in the Premier League come to an end against Chris Wilder's relegation-threatened Blades
Former Manchester United defender Rio Ferdinand singled out Anthony Martial and Marcus Rashford for criticism after the Reds slumped to defeat at the hands of Sheffield United on Wednesday.
Ole Gunnar Solskjaer's men went into the game in fine form, having knocked arch-rivals Liverpool out of the FA Cup at the weekend and on the back of six wins and three draws in their last nine Premier League outings.
That run has seen United jump into title contention, but they missed the chance to reclaim the summit as the Blades secured a shock win at Old Trafford - only their second of what has been a dismal league season to date.
Kean Bryan and Oliver Burke were on target for Chris Wilder's struggling side, scoring either side of Harry Maguire's equaliser which gave the hosts brief hope of a comeback.
United are still only a point off leaders Manchester City, but Ferdinand was not happy with what he saw - particularly in attack.
"They didn't have that zip about them. From minute one, really, there wasn't that cut and thrust we've seen from United," Ferdinand told BT Sport after the final whistle.
"Credit Sheffield United, Chris Wilder set them up very well, but United didn't ask the questions. Bruno Fernandes, who they've relied on so heavily in recent weeks, months, didn't get it going today. Paul Pogba the same.
"If anybody was starting to get carried away at Old Trafford, with the position that they're on, it was a reality check. I think recently Man Utd, in terms of reaction, have been brilliant but tonight it seemed to come crumbling down.
"Rashford and Martial were invisible, didn't get on the end of anything, didn't create anything."
Ferdinand continued to warn that, despite the club's lofty league position, Wednesday's setback should serve as a reminder that reclaiming the Premier League title last won in 2012-13 will be no easy task.
"If anybody was starting to get carried away at Old Trafford, with the position that they're on, it was a reality check," the ex-England star added.
United return to action in the Premier League on Saturday, when they visit Arsenal at the Emirates Stadium.