Nani broke the deadlock late in the second half before Javier Hernandez scored a quickfire second, but Jobi McAnuff restored faith for the away side inside the final 10 minutes.
Nemanja Vidic and Co. held on for an uplifting win, but what can we take from the game?
Here are five tactical observations.
There was nothing fancy about how Brian McDermott set up his troops at Old Trafford on Monday night, but if you're a smaller club that's not often necessary.
What was refreshing was a manager who approached an unbelievably tough game and said: "let's give it a go."
He set up an ambitious 4-4-2 formation with Adam Le Fondre and Noel Hunt in true striker's roles. Mikele Leigertwood and Jem Karacan were asked to shoulder the midfield and to be fair, the Royals played very well for 65-70 minutes of the game.
Contrast this to Aston Villa last season, who under Alex McLeish set up the most negative 4-5-1 football has ever seen despite it effectively being a "free shot."
It's pretty rare, in top-flight football, that you'll see two teams face off using the 4-4-2 formation.
This was one of those rare occasions. Brian McDermott's pure 4-4-2 faced off against a Sir Alex Ferguson side minus the intricate movement of Robin van Persie and Wayne Rooney but with the static, on-the-shoulder presence of Javier Hernandez.
This made for several things, but most of all it was a purist's battle of football—identical shapes, similar strategies.
Who's the better side?
Manchester United fans adore Anderson, but he's simply never going to grow into the player we know he could become if he isn't given a proper chance.
He's used sporadically by Sir Alex Ferguson and that's stopping the Brazilian from gaining full fitness. He's an explosive, box-to-box presence with the potential to form a superb partnership with Tom Cleverley.
Mentally, he's there. Physically, he's not. He can't produce those lung-busting runs that would make him a hero if he can't make it past 60 minutes.
He gets injured, yes, but when he's fit, stick him straight back in. He'll overcome it eventually.
Adam Le Fondre doesn't like this talk of being a super sub. Unfortunately for him, he's so super at being a substitute that he won the Barclay's Player of the Month Award...without starting a single game.
This game was perfect for Brian McDermott. A risk-free scenario to give the former Rotherham United striker a start and see if he can do the business for a full 90 minutes.
It's easy to see why, and for him not to pull up any trees was a highly predictable outcome. He's not an elite player, and he excels when coming on against tired defences.
He's a lower-league predator whose bread and butter is 18-yard box finishing, but that's not enough in the Premier League. A striker has to be able to contribute more than this, and Le Fondre has much to learn.
What has happened to Antonio Valencia?
Last season the Ecuadorian winger totaled 13 assists in the Premier League alone, but this season he's completely off the boil.
Renowned as one of the better crossers in world football and a hark back to the traditional No. 7s roaming our touchlines, he seems to have become too predictable and his accuracy has dipped severely.
He's still getting himself into fantastic positions, but he's also making bad decisions and overthinking things.