In order to counter Chelsea's formation, Avram Grant went with a 4-3-3 of his own, using Mark Noble, Jonathan Spector, and Thomas Hitzlsperger in the midfield with Freddie Sears and Demba Ba flanking Carlton Cole up front. This 4-3-3 frequently looked like a 4-4-2, mainly because Spector seemed to have no idea what was going on and Sears was repeatedly forced to drop back to cover the runs of Ashley Cole.
Chelsea essentially won the central midfield battle before it began - without Scott Parker the Hammers simply couldn't cope with the Frank Lampard-Michael Essien-John Obi Mikel trio. Spector was theoretically picking up Lampard and doing a pretty awful job of it, which took him more or less out of the game without slowing the England midfielder down any, and neither Hitzlsperger nor Noble really did an effective job of closing their direct opponents down. On the other hand, at least they found some space to play in.
What that all meant, of course, is that West Ham had to avoid the centre of the pitch like it was infected with Ebola. There were two main strategies here. The first, which was hilarious ineffective, was to use long balls to Carlton Cole, who would theoretically knock them down for Ba or Sears to run onto. This didn't work at all - David Luiz and Mikel were routinely getting to those long punts first and retrieving possession, which meant that every West Ham attack in the early going would turn into a Chelsea ball the instant it arrived in the home half.
After about twenty-five minutes of this, Grant switched things around and opted to start hitting the Blues down the flanks, taking particular advantage of Branislav Ivanovic's absolutely woeful performance out on the right. With Ivanovic having an off-day and Salomon Kalou being distinctly unhelpful on the defensive side of things, the Chelsea right was open to West Ham and they took full advantage, pushing left back Wayne Bridge high up the pitch and generating several chances in the first half down that wing.
Florent Malouda's failure to score with two early chances was also forcing Chelsea to press Ashley Cole high up on their left, which gave Sears ample opportunity to scamper down that flank more or less unopposed. West Ham did a good job of using their advantage of width in the first half, especially on quick breaks, and could easily have taken the lead when Cech had to save well from Jonathan Spector's diving header. After the hosts took the lead this was less of an issue, however.
By halftime, the pitch had become such a mess that sensible buildup play became almost impossible, although Chelsea soldiered on with it pretty well for the first fifteen minutes or so. By about the seventhieth minute, however, passes were becoming less and less accurate on the extremely wet surface and West Ham were able to mount quick, chaotic attacks on the transition. It was this flurry of chances that's led people to imply that Chelsea somehow didn't deserve a 3-0 win, but when you look at the passing figures you get a slightly different story.
Figure 2: Chelsea vs. West Ham United passing, 4/23/2011. Powered by Tableau.
Chelsea's starting midfield three completed five fewer passes than the entirety of the West Ham team - and that's despite Michael Essien leaving after 57 minutes.By the 33rd minute, Chelsea already had more complete passes than West Ham would manage all evening. We haven't seen that sort of dominance in possession by Chelsea for a long time - they ended up completing almost two passes for every one made by the visitors.
You can see the impact of Kalou and Ivanovic having a bad day here too. It's no surprise to see Hitzlsperger and Bridge, the two players on the left flank West Ham, at the top of their team's passing chart (although we should note that they are both behind Mikel, Malouda, Lampard, Essien, Cole, John Terry, Ivanovic, and David Luiz). Incidentally, Mikel on his own (with 95/104) completed more passes than West Ham's top three combined.
When we looked back at how passing numbers effect goals scored and conceded, we found a strong relationship between midfield passing and wins, and indeed if you tallied up the chances on Saturday's match you'd find them strongly tilted in Chelsea's favour. My best explanation as to why we're being told the scoreline was undeserved was due to the stress of those West Ham chances - they should have been put away and the game should have been level. Of course, Chelsea should have been three or four ahead at that point and the game shouldn't have been anywhere close to level, but that would be ruining the narrative, wouldn't it?
Figure 3: Chelsea vs. West Ham United location data, 4/23/2011. Powered by Tableau.
It's interesting to see how well West Ham defended as soon as the ball got to their final third. They managed five tackles, 12 interceptions, and won four aerial duels there for 21 turnovers in their defensive third, compared to 13 everywhere else. Some of this is because Chelsea were forcing the play inside at that point, especially on the left, where Malouda was cutting inside like his life depended on it. Manuel da Costa, however, was a major stumbling block, and he accounted for the bulk of those turnovers as the Blues tried to play through him to no avail.
All in all, the match looks to me like a tale of more or less total dominance in the most important area of the pitch combined with initial bad luck with finishing. Yeah, there were enough scary moments in the game to make it more stressful than we would have liked, and Chelsea had some obvious weaknesses that West Ham were trying to hit, but an emphatic win is really no more than what they deserved.