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* A match to truly highlight how far United have fallen, and how shaky this side currently looks defensively. It wasn't even that David Moyes' side played particularly poorly for large periods, but they were still left utterly demoralised. United were not outclassed, but out-fought and out-thought, although that will provide little consolation to fans after a seventh Premier League defeat of the season. Even with 16 games remaining, that's as many as they have lost in each of their last nine seasons.
Chelsea looked sluggish at times, particularly during the first half, and yet finished it 2-0 up thanks to two moments in which concentration was found lacking in the visitors' defence. The best teams simply don't commit such errors.
It is these crucial moments, on which games and titles are decided, that United have fallen critically short. The split-second decision to cover the run of your opposite number, the accuracy of that final ball or the opportunistic finishing of a chance - these are the incidents that decide the haves and have-nots. On almost each and every one, United are falling short.
* After being overlooked for the manager's job at Old Trafford, this victory will have had a certain shine for Jose Mourinho - I think we can be sure enough of the man's ego to make that conclusion. That it was his 100th Premier League victory (comfortably quicker than any other manager in Premier League history) against the same (and lofty) opponents as his first will have made it all the more sweet.
His Chelsea side have also looked utterly ruthless in the big games this season, gaining exactly what they want from the important matches. Draws away at Spurs, United and Arsenal, and victories at home to Liverpool, Manchester City and now United. It's ominous stuff with big games to come at Stamford Bridge.
There has been a great deal written this week about whether Mourinho should have been chosen as Alex Ferguson's replacement (and such sweeping judgments are far easier to make in hindsight), but the majority opinion seems to be that it became a choice of long-term project vs short-term success. The choice of the former over the latter looks shaky right now, and the pertinent question must remain - would Jose Mourinho have this United side in a higher position than their current place of seventh, 14 points behind the leaders.
United fans taunting the Portuguese for being overlooked during early periods of the match were noticeably quieter once their side conceded the third goal. I'm not saying this 90 minutes has changed their opinion, but it sure focuses the mind on that particular issue.
* Moyes didn't help himself with his selection. The first big call, dropping Darren Fletcher back down to the bench in favour of Phil Jones and Michael Carrick in midfield, could be seen as permissible given Fletcher's substantial lay-off. Scotland's captain is yet to play in a game of this magnitude since his return, and only Moyes will know how recent fixtures have fatigued him.
His other decision was far more debatable. Cesar Azpilicueta has been mightily impressive of late but playing a right-footer at left-back always raises the risk that they may struggle against tricky feet and pace on the wing, exactly the characteristics boasted by Adnan Januzaj.
Instead of allowing Januzaj free reign to take on Azpilicueta with Kagawa in the middle, Moyes opted to operate Januzaj in the most advanced role, with Antonio Valencia on the right and Ashley Young on the left. It was uninspiring at best.
* It may not have proved totally effective, but the positioning of Januzaj as the focal point of attack is a huge fillip for the youngster. His performances may have justified such faith, but you still have to take a step back and consider that such is the level of the teenager's ability, he was picked as the lynchpin of one of the world's biggest sides in one of their biggest games of the season. At 18 years of age.
It's an enormous compliment, and whilst Januzaj struggled to make an impact in the latter stages, his effervescence in the opening periods of the match allowed United to create. The principal concern must now be holding on to their newest star if the promise of Champions League football fails to materialise.
* Despite pre-match reservations over United's tactical set-up, it was clear which side opened the game better. The visitors were quick out of the blocks, perhaps aided by the element of surprise in Chelsea seeing Januzaj so far forward. In the first ten minutes Chelsea saw just 22% of the ball as United racked up 67 passes in comparison with Chelsea's 22. Samuel Eto'o touched the ball just twice in the first 15 minutes.
And then came the bolt out of the blue, courtesy of Eto'o's third, fourth and fifth touches.
Whilst it was a cruel deflection from the Cameroonian's shot off the toe of Michael Carric, that gave David De Gea little to no chance, the damage had been done through the weakness of Phil Jones. Evidently chosen as the anchor in midfield in order to cope with the threat of Chelsea's attacking midfielders, one of the most basic remits would have been not to commit himself into the challenge unnecessarily.
Jones fell far short of that task. He may have expected Eto'o to take the ball to the touchline on his right foot and lay it back for a team-mate, but the placement of his weight onto his left side made it easy for Eto'o to leave him looking rather foolish indeed.
It once again forces the question to be asked - where is Jones' best position? In commentary, Gary Neville stated his belief that centre-back is his eventual destination but, having played just five of his 18 matches there this season, is there any indication that Moyes shares Neville's view?
Instead, the majority of Jones' appearances this season have been in central midfield, a position that Jones is surely unlikely to make his own on the evidence of Sunday. It may seem harsh, but Jones will be judged on such occasions. There is a very real danger that he could become tarnished by the 'Jack of all trades' tag.
* If the defending for the first goal left much to be desired, things went from bad to worse before the break, when Eto'o was again left free in the area, this time following a set piece. Whilst Antonio Valencia was initially tasked with marking Eto'o (a bizarre choice in itself given United's height with Jones, Vidic, Evans and Carrick), when the corner was cleared he ventured out.
The responsibility then fell to Rafael, who can be seen on the replays looking straight at the Chelsea forward. However, rather than sticking tight to his man (or at least putting pressure on him), the Brazilian was left standing on the penalty spot as the striker made it 2-0. United fans will be getting sick of the sight of Vidic standing with arms raised, questioning why he has been left alone to thwart danger.
It got no better for the third. With Valencia again tasked with sticking to Eto'o (although arriving remarkably late to carry out his duties), the Ecuadorian proceeded to simply hold his opposite number without any designs on clearing the ball. Whilst that is a tactic used more and more on set pieces recently, it only works if you actually stop your opponent getting to the ball. Valencia didn't, and that was that.
"We got unlucky for the first goal but after that we conceded from two set-pieces. That's our own fault, no-one else," was Moyes' post-match assessment. "That's been the difference today."
* If the debate over David Moyes' selection and strategy is open to debate, Jose Mourinho typically made the perfect call with his big decision. With two goals in his last three games, many would have expected Fernando Torres to have got the gig up front, but Jose instead plumped for one goal in seven Samuel Eto'o. The striker repaid the faith impeccably.
It is 16 months since Eto'o last scored more than once in a league game (against FK Krasnodar, if you're asking) and his last hat-trick was in September 2010, but he delivered at the perfect time. His manager will have been convinced that he can be relied upon for future assignments.
As an aside, remember when Chelsea strikers didn't score goals? That's now six goals in four games from any of Chelsea's trio of forwards.
* Young was utterly average, as ever. His 56 minutes provided one shot, on two minutes when he fired straight at Petr Cech when given a clear sight of goal, no chances created, four crosses and a yellow card borne out of frustration .
However, it is Young's incessantly poor delivery that most frustrates. After just a few minutes he was caught offside from his own corner (isn't that something that players think about?), and time and again his crosses were simply headed away by a grateful defender at the front post.
Young is an international footballer (and if his 30 England caps don't make you cry then nothing will) and has commanded fees above £25million, so I refuse to believe that I am being too harsh. Surely as a winger we should expect some exuberance, some verve, some excitement?
Young's selection at the earliest possible opportunity following his shoulder injury is the perfect epitome of United's current dirge - uninspiring, predictable and dramatically short of the required quality.
* Young's selection must also act as a firmly hammered-in nail to the coffin of Shinji Kagawa's Manchester United career.
Kagawa had one of his better games for United against Swansea last weekend, and surely merited a place in the side? He has so evidently not impressed sufficiently when farmed onto the left wing during his United career, but surely still offers more than a winger whose only moves are to cut inside and pass or throw himself to the ground. Neither are particularly useful tactics.
It may sound hyperbolic, but there is a line of thought that once you are demeaned below Ashley Young in the pecking order for the biggest matches, you might as well start looking for a new club. Kagawa may well feel like doing just that.
* There is a reasonable argument to suggest that Eden Hazard is the best attacking midfielder in Europe on current form, but United's determination to thwart his threat was largely successful. Instead, the real midfield star was Willian.
Mourinho received plenty of criticism for his ignorance of Juan Mata for large periods this season, partly because Mata is so bloody lovely and partly because we like to think that we know best. Quite obviously, Jose does.
Willian is everything that Mata isn't, and that is not meant as an insult to the Spaniard. The Brazilian harried and hustled and pressed during a first half in which Chelsea were often second best. He is part of a new breed of attacking midfielder who operates in a dual role, expected to assist in defence from an advanced position. He made more tackles than nine of his team-mates, and gained possession from opponents more than the same number. When this is combined with touching the ball more than any other attacking Chelsea player and also making more passes, it is clear to see that Mourinho has recruited an all-action footballer.
After the outrage at Mata's exclusion at Chelsea, the realisation dawns that it was both justified and has been vindicated. Mourinho has been proved right - as if there was ever a glimmer of doubt.
* In the first 20 minutes David Luiz demonstrated exactly why Chelsea have chosen to spend £21million to bring back Nemanja Matic. It is not that David Luiz is a poor player (far from it, in fact) but his tendency to make rash decisions leaves him open to criticism.
The challenge on Antonio Valencia on the near touchline drew a booking alongside the customary complaints from Chelsea's players, but the replay showed just how foolish those protestations were. The Brazilian barged into Valencia without any hope or desire of playing the ball, and gave himself 70 minutes to walk on a tightrope.
Ten minutes later, and we had another example of Luiz's impatience. Sat in behind Januzaj on the left edge of the penalty area, the midfielder committed to winning the ball when all he needed to do was shield the United player away from goal.
The signing of Matic provides Mourinho with reliability over extravagance. The Sky coverage picked up on the Portuguese's urges for Luiz to hold rather than venturing forward - Chelsea's manager is unlikely to have much patience given the extra weapon at his disposal, and Matic is a far more attractive option than Jon Obi Mikel.
* There is an issue which is really beginning to bug, so humour me. When the ball fell at the feet of Danny Welbeck in the United penalty area after a clever pass from Adnan Januzaj, many expected him to finish the opportunity. That he failed do so was largely thanks to the presence of Azpilicueta, and by 'presence' I mean a kick to the back of Welbeck's heels.
As Welbeck got his shot away (which was scuffed and easily saved), no penalty was given, as is tradition. But replay that incident anywhere else on the field, and a free-kick is undoubtedly awarded, and accepted.
It appears that whilst being late in the challenge elsewhere on the pitch is deemed as a foolish practice, in the penalty area tardiness actually pays.
* Although Chelsea never seemed in any grave danger of ceding their lead once Eto'o had completed their hat-trick, their willful slowing of the tempo did create a self-imposed problem. David Luiz was effectively utilised as a hoofball merchant, looking long whenever he received the ball, and often clearing into the stands.
Doing so simply invited United onto them. Javier Hernandez was afforded too much time on the ball, as was Januzaj, and United created numerous situations of danger after their eventual consolation. Had Hernandez's goal come ten minutes earlier, we may have had a finish to rival the one in February 2012, when United came from 3-0 down to draw.
It is far easier to lower the tempo than raise it, and whilst Mourinho will consider it a worthwhile risk in order to save legs for future matches, by the end of the game they had David Luiz, Ramires, Mikel and Matic all on the field. Four holding midfielders may close out a match effectively, but it doesn't make for a particularly stimulating finish to a match.
* Artur Boruc will have been sat at home fuming watching Petr Cech inexplicably get away with his attempted Cruyff turn. The reaction from his manager (hands over face, cursing) should persuade Chelsea's no. 1 not to aim to repeat the trick.
* Sometimes you really do wonder about professional footballers. Nemanja Vidic is an international. He has played more than 200 Premier League games for Manchester United and is the captain. One can understand the frustration felt at the current situation, but to dive in for such a wild challenge is nothing but an immature and needless move.
There could be an argument for it being a booking, but to me it almost represented violent conduct. Much like the challenge from Mapou Yanga-Mbiwa last weekend, there was clearly no attempt to play the ball, instead halt an opponent that had left you beaten in the most cynical manner available. The ball was at least two foot away.
Speaking of two feet brings us nicely to Rafael, who was incredibly fortunate to remain on the field. Having completely lost his head, it was evident that the Brazilian deliberately jumped in with two feet from the floor. We have had assurances from the officials that these are the type of challenges that are worthy of red cards, reckless and without possible means of control. The booking received should protect him from further punishment, but for that the law is an ass.
And so now, Vidic will miss three games when United need him most. The squad must rally round each other and prepare for a cup semi-final second leg that may provide United with their only opportunity at silverware. That they will take on Sunderland (plus Cardiff and Stoke) without him, owes much to the idiocy of their captain.
* Sympathy may be rare for David Moyes, but let's end with some. One has to point out the manager's misfortune over the loss of both Robin van Persie and Wayne Rooney. Last season, of the 24 matches that the pair both started in all competitions, United won 19, drew four and lost just one.
This season, Moyes has been without one or both of his striking options for 14 league games out of a possible 22. United have taken just 17 points from these 14 games. Conversely, in the eight league games in which the two have featured, United have won six and drawn two. That's a difference of 1.3 points per games, or 59 points over a season. Sink or swim, effectively.
Daniel Storey - follow him on Twitter
"I find it ironic how some Manure fans think Chelsea's goals came by mistakes" -------------- What's ironic about it? I'm not sure that "ironic" is the word you're looking for. You may disagree, and that's fine. But it's not "ironic". Not that I can see, anyway.- HarryBoulton