A very bad day at the office
In what became an extremely comfortable win for Chelsea, Manchester United started promisingly. For the first 10 minutes, they pressed well and dominated possession. However, once Samuel Eto'o's goal went in, United's bright start collapsed, just as it did when he scored the opener for Barcelona in the 2009 Champions League final.
Here are six things we learned from United's performance. Spoiler warning: It's not great news.
Not the man for Moyes' big occasions.
The decision to start with Ashley Young on the left and Adnan Januzaj solidifies the impression that Shinji Kagawa remains outside the circle of David Moyes' trust.
Young was preferred presumably for the extra cover he provides Patrice Evra, although both of Chelsea's first-half goals came from attacks down the left.
Young almost rewarded Moyes' decision early in the game, combining excellently with Welbeck and forcing a good save from Petr Cech. However, as the first half wore on, United lacked attacking guile, except when the ball came to Januzaj.
It is far from clear that the inclusion of Kagawa would have made a significant difference to the outcome of the match, but Moyes preferring Januzaj, who played virtually as a second striker in the first half, through the middle and Young on the left, in such a big game, is further illustration of Kagawa's place in the pecking order.
I don't think he expected that...
United fans have long bemoaned the absence of quality and quantity in central midfield. However, today's result pivoted on key defensive errors. Phil Jones was turned all ends up by Samuel Eto'o for his first.
Rafael's casual jog back towards his position, whilst the second ball came back in for the second, left a hole big enough for most of Chelsea's back line to stroll through.
For the third, Jonny Evans was unable to stay with his man, leaving a free header for Cahill that led to the goal.
Compounding this, Nemanja Vidic's late challenge may not have warranted a red card, but as the cliché goes, he "gave the referee a decision." Reckless in his unprofessionalism, if not actually dangerous, United's captain has earned himself a three-match ban that United simply cannot afford.
Moments later, Rafael received a yellow card for a two-footed studs-up challenge that absolutely deserved red.
A very poor showing from United's rear guard.
Does Jose still want the United job?
There has been a suspicion amongst the fanbase at Old Trafford that perhaps the respect he showed United when managing Real Madrid might evaporate now that hostilities have resumed.
However, his demeanour remains largely unchanged. Acknowledging the away support as they sang about his presumed desire for Moyes' job, he also offered an apology to Moyes when he strayed into his technical area whilst relaying orders to David Luiz.
Not that he wanted to be in that technical area rather than his own, of course...
The boy who can do anything.
I waxed lyrical about the player United fans call "the boy who can do anything" earlier in the week. Even having written all that, I was still very impressed that Januzaj appeared entirely unmoved by the increased quality of opposition.
Given the injuries that have wreaked havoc on United's forward line, Januzaj's importance has been enhanced to the point where he is consistently United's best option to provide a moment of magic or the key to unlocking a stubborn defence.
The dribble past David Luiz, an experienced and wily opponent, showed just why United fans are so quick to sing Januzaj's name.
Young forces a decent save from Cech
This is not the first game in recent history in which United have started brightly and then faded badly. The Champions League finals in 2009 and 2011 against Barcelona are the examples that come quickest to mind, but it is a pattern of play that has been oft repeated.
Today, United absolutely dominated the opening exchanges but were not able to make that pressure tell, and once Chelsea had gone in front, United were unable to recapture that early momentum.
If United had managed to make more of their excellent start to the game, it could have been a very different affair.
Javier Hernandez has been struggling to make an impact this season. It is nice to see that playing against Chelsea still brings out the poacher's instinct in him, given his extraordinary scoring record against them.
The goal offered scant consolation to the United faithful, but perhaps he will be able to use this as a platform on which to build for the remainder of the season.