The story going into this game was one of contrasting fortunes. Chelsea had made a stunning start in their bid to secure the 2014-15 Premier League title, having won 22 points from a possible 24 over their opening eight games.
Had Man Utd lost this match it would have been their worst start to a league campaign for 25 years.
Unsurprisingly, then, Chelsea had both scored more and conceded fewer than Man Utd coming into the match. The London team had netted 23, the most in the league, and let in eight – second only to Southampton's five.
The same statistics for Man Utd read: scored 15, conceded 12.
Both teams suffered from limitations to squad selection that prevented them from deploying what would generally be considered a full-strength lineup. Wayne Rooney was still serving a suspension for a red card against West Ham, while defenders Phil Jones and Johnny Evans, and midfielder Ander Herrera were on the injured list.
Despite being forced to play third-choice striker Didier Drogba, Chelsea went into the game as favourites.
Fellaini and Mata shut down Fabregas and Matic
Leading up to this game, the partnership of Cesc Fabregas and Nemanja Matic had arguably been Chelsea's greatest strength. Fabregas had been involved in eight goals over the previous eight games, notching up seven assists and netting one.
A big part of his success has been the discipline of Matic playing alongside him, the Serb filling the gaps whenever Fabregas gets forward and acting as an outlet for those times when attacking passes are either not available or too risky.
Clearly, shutting down the formidable Matic/Fabregas partnership is one of the key pillars to defeating Chelsea. Van Gaal attempted to do this by playing Marouane Fellaini and Juan Mata in orthodox central midfield roles ahead of the defensively-minded Daley Blind.
In the first half, Fellaini and Mata's primary job was to stick as close as possible to Fabregas and Matic. The two Man Utd midfielders kept to their opponents so diligently that to watch them keenly was akin to watching a man-marking training session.
The effectiveness of the approach, however, was significant. Whenever one of the Chelsea midfielders found themselves in possession they had extremely limited time to find a pass upfield or out to the flanks. Fellaini and Mata were happy to allow them to pass backwards, but other angles were aggressively shut down.
Chelsea created eight chances throughout the game, only two of them coming from central areas – both of those coming during the opening 15 minutes of the second half. At this point the game had opened up slightly and Fellaini, in particular, was given more freedom to join Van Persie in attack.
As a result of the lack of space, Fabregas and Matic began to drift away from their designed positions in a bid to influence the game elsewhere. This resulted in a wider gap opening up between Chelsea's midfield and defence, creating channels within which Robin van Persie and Adnan Januzaj could operate.
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Helped by the tireless overlapping runs of Luke Shaw, Man Utd found themselves in dangerous positions along the left side often. Had goalkeeper Thibaut Courtois not been in such (predictably) excellent form, Chelsea could have easily found themselves behind at half time.
Effectively, the first half saw Man Utd purposefully negate much of their own central attacking threat by focusing so strongly on shutting down Fabregas/Matic. Man Utd's lack of penetration through the middle was then compensated for by overloading on their left side.
The approach allowed Man Utd to grow in confidence and gain a foothold in a game that few thought they would be able to control.
Drogba takes up old-fashioned 'target man' role
For most capable teams, certainly those with title aspirations, the era of the target man is dead – modern defensive systems are easily capable of overcoming such a threat. However, in the absence of Remy and Costa, Drogba proved that the traditional target man still can continue to impact the modern form of the game.
Drogba would drop deep into midfield frequently, especially when the ball was at the feet of Chelsea's defenders. With Matic and Fabregas usually covered, Drogba's position provided an outlet for defenders to use to relieve pressure.
The comparative height of Man Utd's central defenders, one of which would almost always follow Drogba towards the centre circle, meant that the Chelsea forward won most of his aerial duels.
Winning these battles led sometimes to direct flicks into the feet of the advancing Willian or Hazard, at other times it allowed the Ivorian to slow down play and allow Ivanovic and Fabregas to get forward.
Drogba's coming deeper meant that he spent a significant amount of time behind play, with Hazard and Willian leading the line by cutting inside from wide areas. In the second half, with Chelsea better able to wrestle control of central midfield away from Man Utd, the full-backs were also given more encouragement to join the attack.
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Hazard most obviously benefited from Drogba coming deeper, the space created along the defensive line giving him ample running room. The Belgian's superb dribbling ability makes him dangerous with the ball at his feet and he was allowed to run at centre-backs directly, facilitated by Drogba's movement and flick-ons.
Only a good save from David de Gea prevented Hazard scoring following an excellent piece of link-up play with Drogba. That save produced the corner that led to Chelsea's goal.
The downside to Drogba coming deeper was that Oscar found space difficult to come by. Not a natural striker, Oscar was unwilling to run ahead of Drogba and look to occupy the central areas around Man Utd's box.
With one of the central defenders taking up the job of challenging Drogba, Blind was free to stick to Oscar and make it difficult for him to pick up the ball. The flanks being occupied on one side by Luis/Hazard and on the other by Ivanovic/Willian, the Brazilian had very little means of influencing the game consistently.
It came as no surprise then that Chelsea's first substitution, on 66 minutes, saw Oscar replaced by John Obi Mikel. With Oscar posing very little threat offensively, and Chelsea having gone a goal up thanks to Drogba's headed goal on 52 minutes, it made defensive sense for Jose Mourinho to replace him.
Chelsea attempt to manage game rather than kill it
Following their early second-half goal, Chelsea switched gears and set about trying to manage their lead rather than secure the win by pushing for a second.
The swap of Oscar for Mikel naturally gave the team a more defensive edge, but they also stepped up their physicality in an attempt to disrupt Man Utd's passing rhythm and prevent breaks from midfield. This point is demonstrated by the fact that they managed to accumulate five yellow cards in the second half, rounded off by Ivanovic's eventual dismissal.
Chelsea were content to allow Man Utd's centre-backs time on the ball, the duo of Chris Smalling and Marcos Rojo barely coming under any pressure whatsoever. As he does regularly, Blind dropped between the two centre-backs – giving licence for Rafael and Shaw to push forward up the touchlines without losing defensive muscle.
Blind, a danger thanks to his comparatively superior passing ability, was closed down by Chelsea doggedly. In the second half Matic was especially adept at this task, making his presence felt far more after Drogba's goal – helped by the fact that Fellaini took up a more offensive position in an attempt to even the score.
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The Man Utd full-backs were closed down instantly, too. In particular it was the forward runs of Shaw down the left that Chelsea were hoping to halt, his partnership with Januzaj, and occasionally Di Maria, causing problems all game.
By allowing Smalling and Rojo time on the ball, Chelsea were hoping to entice the duo toward the halfway line, constricting the amount of space between Man Utd's front and back lines. In turn, this allowed Chelsea to make the pitch 'small' and make it easier for each defender to patrol their zone and look to play the offside trap.
The tactic worked, Man Utd looking like a shadow of the team they were in the first half and highlighting just how impactful Matic can be when he's left free to disrupt the opposition.
Set-piece confusion causes havoc
One of the most confusing battles of the game involved Rafael man marking Drogba during attacking set pieces. Nearly six inches separate the two players... a complete mismatch.
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Given the frequency with which Rafael glued himself to Drogba it seems that Van Gaal and his coaching team had come into the game with exactly this plan in mind. Man Utd paid for it from a corner on 52 minutes following De Gea's save from Hazard.
Running towards a corner aimed at the near post, Drogba created significant separation between himself and Rafael by nudging the Man Utd defender just prior to starting his run. By the time Drogba had positioned himself to deflect the ball into the net, Rafael was firmly in no-man's-land behind the striker.
More success defending the corner might have come from sandwiching Drogba between two players, preventing him from getting a clear run to the near post and covering any (unlikely) pull towards the back post.
Another strategy might have been to assign the taller Van Persie to marking Drogba. This would have reduced Man Utd's counter-attacking threat but would likely have made life more difficult for Drogba. Chelsea were the bigger team, so it was impossible to neutralise their aerial threat in its entirety. Surely, however, Drogba should have been singled out as a top priority.
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Later in the game Chelsea's physical play finally caught up with them in the form of Ivanovic's red card, the resulting free kick providing Man Utd with an equaliser deep into stoppage time.
The sending-off proved devastating for Chelsea, their inability to defend the free kick into the box allowing Van Persie to pick up the scraps and score. It's impossible to say whether or not Ivanovic would have been able to prevent the goal, but it's safe to assume that his involvement would have made it more difficult for Man Utd to achieve the two unchallenged attempts at goal they got from the set piece.
Man Utd ended the game with 10 more shots than the visitors, as well as slightly edging the possession and passing numbers. However, given the fact that Chelsea's defensive ideology in the second half intentionally limited their own attacking threat, a draw was a fair result.
12 Mins – Yellow Card, Man Utd: Rafael struggles to contain a run into space by Hazard, pulls him to the ground to negate the danger and deservedly goes into the book.
21 Mins – Yellow Card, Chelsea: Mata looks to counter attack from inside his own half but is tripped by Drogba. A professional foul.
38 Mins – Yellow Card, Chelsea: Heavy challenge from Matic on Van Persie.
50 Mins – Yellow Card, Chelsea: Chelsea's first yellow on the half shown to Fabregas for foul on Mata.
52 Mins – Goal, Chelsea: Drogba takes advantage of Rafael's inability to properly mark him and scores at the near post from a corner kick.
62 Mins – Yellow Card, Chelsea: Increasingly physical play from Chelsea sees Oscar punished for a foul on Smalling.
65 Mins – Substitution, Chelsea: John Obi Mikel brought on to replace Oscar as Mourinho opts for an overtly defensive approach.
66 Mins – Substitution, Man Utd: Van Gaal reacts to Chelsea's defensive structure by bringing on forward James Wilson in place of Mata. Wilson's presence, in the face of Chelsea's disciplined formation, goes largely unnoticed.
77 Mins – Yellow Card, Man Utd: The Man Utd midfielder is cautioned for pulling Hazard back.
87 Mins – Yellow Card, Chelsea: Hazard's turn to go into the book for a foul on Rafael in a dangerous wide position.
89 Mins – Substitution, Chelsea: Time wasting exercise as Hazard is replaced by Andre Schurrle.
93 Mins – Red Card, Chelsea: Ivanovic trips Di Maria on the edge of the box to get himself sent off.
93 Mins – Goal, Man Utd: Free kick resulting from Ivanovic's foul leads to Van Persie scoring from close range following Courtois's save from Fellaini's initial header at goal.