Many expected the Red Devils to still be feeling the effects of their unfortunate exit from the Champions League midweek, and for much of the game, such would be a fair comment.
Javier Hernandez and Wayne Rooney scored the goals for Sir Alex Ferguson's side that earns them an unwanted replay.
Here are the full player ratings for United:
David de Gea: 7
He was relatively untroubled until Chelsea's furious second half fightback started.
The Spanish keeper will perhaps be disappointed not to have prevented either Chelsea goal, but he redeemed himself with a stunning late stop to deny Juan Mata a certain goal, saving with an outstretched boot.
The Brazilian right-back was a lively threat going forward but was perhaps caught out of position several times on the back foot.
After some terrific recent displays, Rafael remains the Red Devils' No. 1 option in the position, no matter what happened Sunday.
Rio Ferdinand: 7
In front of a watching Roy Hodgson, Rio Ferdinand was his side's most reliable defender against Chelsea, heading away countless crosses and making some crucial blocks.
He was a huge step ahead of Gary Cahill, who seems to hold the edge over Ferdinand when it comes to the England setup.
Jonny Evans: 5
There can be little doubt that Jonny Evans has been one of United's most improved players this season, but against the Blues, his performance was very underwhelming.
Too often he was turned inside out by the likes of Juan Mata and Ramires.
Patrice Evra: 6
Like Evans, Patrice Evra will have little to boast about regarding his defensive display on Sunday.
The Frenchman was a marauding threat down the right flank, though, providing an attacking purpose when Wayne Rooney and Shinji Kagawa moved inside.
Michael Carrick: 7
The holding midfielder provided one of the passes of the season for Javier Hernandez's opener, dinking a terrific pass over the Chelsea back line for the Mexican to head home.
Apart from the odd sloppy error, he was United's most consistent player in central midfield, distributing the ball with a typical ease.
Tom Cleverley: 6
Another big game, another start for Tom Cleverley, who is fast becoming a regular in Sir Alex's team for the biggest games.
He was involved in much of United's best passing sequences Sunday but was outmuscled by Ramires and David Luiz a few too many times.
Nani's withdrawal from injury was seriously damaging to his team's chances against Chelsea. For much of the first half, his skill and vision proved terrorising for the Blues' back line.
Twice in one week, he has had to walk down the Old Trafford tunnel prematurely—a week he would sooner forget.
Wayne Rooney: 6
Who else but Wayne Rooney should score, given the hoopla that has surrounded his rumoured exit from Old Trafford this week?
Overall, though, he was fairly ineffectual, failing to stamp his name on the trequartista position he usually makes his own.
Shinji Kagawa: 6
Like Rooney, Kagawa's influence on affairs Sunday was limited.
The Japan international was a deserved starter following his sensational display against Norwich last weekend, but this time he failed to find enough space to operate and play his natural game.
Javier Hernandez: 7
A stunning goal marked Chicharito's return to the United starting XI—one that should be included in textbooks on the art of heading the ball.
He was an assured threat in attack when given the opportunity, but too often he failed to receive good enough service to really thrive.
Antonio Valencia: 4
A horrible, horrible cameo from the Ecuadorian winger, whose touch was more befitting a player in League Two than one playing at the highest level.
Robin van Persie: 6
The Dutchman's dry spell in front of goal continued Sunday, as his late substitution failed to pay any dividends.
Danny Welbeck: 6
The introduction of Danny Welbeck to the game saw an increase in pure energy, but little in terms of finesse.
Who did you think was United's best player vs. Chelsea?