Note: The game chart will be after the jump, just so those who don't want to see it don't have to load it on the front page. Also, Zonal Marking covered this game as well.
As Gerard Houllier said, this was a high-quality match that was missing just one thing: Goals. It's probably best to divide the game into quarters in order to figure out what was going on - there was an early spell of Villa dominance followed by a Chelsea-controlled lull, an all-out onslaught following half time, and then a period of total chaos at the very end of the game.
Aston Villa came out of the gate pressing hard from the very beginning. It's a strategy that the team isn't fit enough to keep up for the whole match, but can be very effective in the early going when faced with superior opposition. By hounding Chelsea across the pitch (especially in midfield, where Stiliyan Petrov and Nigel Reo-Coker made complete nuisances of themselves), they denied the visitors the time they needed to compose themselves on the ball and thread passes together. The less experienced Chelsea players on the pitch had the most trouble, but even veterans like Branislav Ivanovic and Ashley Cole were having issues with both identifying sensible passes and completing them.
Pressing hard in the opening stages takes some of the pressure off the defence, but it also can create chances - Stephen Ireland found himself free on goal in the first minute after Mikel lost track of him, and John Carew took advantage of a misplaced pass from Kakuta shortly afterwards - both efforts ended up a couple of feet wide of the far post. Had either found their way in, the game would have looked very different.
Villa lost Richard Dunne fairly early and were forced to re-organise their defence, favouring Ciaran Clark over Carlos Cuellar to fill in at centreback. Dunne's 13th minute departure robbed a little of the momentum from the home side, but not as much as might be expected; the youngster having no trouble keeping possession away from the Blues while feeding his midfield. Slowly, however, Chelsea started to settle down.
Chelsea managed to keep the ball a lot better, partially because Villa were getting tired and partially because the midfield trio of Ramires, Mikel, and Essien were dropping a little deeper to avoid Reo-Coker and Petrov. However, Chelsea's attempted attacks were meeting fierce resistance whenever they entered the final third. Villa's defence was exceptionally well organised, and Petrov, Reo-Coker, and Stewart Downing were all playing deep enough to make Chelsea's path towards goal very congested. As a result, Chelsea were forced to try going down the 'moments of individual brilliance' path, best epitomised by Gael Kakuta spinning brilliantly past Petrov before seeing the ball roll to the waiting feet of Ciaran Clark.
With left-footed Kakuta playing on the right and drifting in and Ashley Cole taking up very advanced positions on the left, Chelsea's attack was completely out of balance. Paulo Ferreira was doing his best to provide an outlet on the right side, but whenever Chelsea attempted to switch the play they did so so slowly that Villa were able to shift Stephen Warnock over to block Ferreira off. With Beye and Downing deep on the left, and Reo-Coker covering, Chelsea weren't able to overload that side despite committing Malouda and Cole to the fray. Instead, the only regularly open player was Michael Essien in more or less the centre of the pitch (Ciaran Clark was naturally reluctant to pop out of defence to close him down), and Essien was used as an outlet on a couple of occasions only to reset the attack or let fly with a very wild shot.
Villa were seeing very little of the ball and weren't looking especially dangerous in possession, but the Blues were similarly toothless and looking less than likely to score despite dominating proceedings for significant portions of the half. Carlo Ancelotti's halftime solution was to withdraw Gael Kakuta and replace him with Yuri Zhirkov.
Yuri Zhirkov was deployed as a left forward, with Malouda given a free role instead of taking up Kakuta's position on the right. His inclination was to stay on the left, and Chelsea were finally able to overload that flank - Cole, Malouda, and Zhirkov is an exceptionally dangerous combination. Villa were forced to drop back even further, which meant that the only way they could possibly get the ball out of their own half was by finding John Carew with long passes. This would have worked better if they were actually getting the ball to Carew, as instead they were usually finding Mikel or Essien, who were able to shuttle the ball left to begin the attack anew. None of the Villa players were coming out to press Chelsea's midfield three, instead ceding possession in the middle third in order to keep the box well and truly packed.
Chelsea were looking very dangerous, and Anelka was starting to link up with Ferreira down the right side as well. Anelka troubled Friedel with a low snap shot and missed a pretty good opportunity well high and wide of the far post, but for the most part attacks were ending with desperate Villa lunges at the final ball. By the 70th minute Houllier was looking for new outlets to relieve pressure while Ancelotti was trying to add even more width to Chelsea as well as finding a more attacking midfielder to deploy in the place of a largely disappointing Ramires. Nathan Delfouneso was Villa's choice, Bosingwa and McEachran Chelsea's.
Delfouneso's pace was allowing Villa to hit passes out of the back down the channels rather than attempting to direct them straight to Carew, which meant that suddenly the game turned into an entertaining back and forth rather than a wave of Chelsea attacks. The woodwork was rattled three times in the final fifteen minutes - Ivanovic and Collins both hit the post off corners, and Anelka managed to spurn a lovely cross from Ashley Cole after excellent work down the left by McEachran and Zhirkov.
McEachran was involved in much of Chelsea's best work towards the end of the game (Bosingwa was barely involved and probably did more for Villa's attack than visitors'), but was nearly responsible for conceding an injury-time goal after he lost the ball to Reo-Coker in his own half. One has to imagine that fans of both teams had their hearts in their mouths for the last few minutes of the game - both teams looked on the brink of scoring several times but just couldn't get it in the net.