As we're all aware, Chelsea's shape last season was very different at the beginning of the season than it was at it's conclusion. The general consensus would be that we started the season in a 4-3-3 and at some point in the latter portion of AVB's reign switched over to the 4-2-3-1/4-2-1-3 that he was sacked while using. That same consensus would then tell you that we then kept the 4-2-3-1 as our primary formation under Roberto Di Matteo, with it simply becoming a bit more conservative in the process. Zonal Marking took a look at this about a month into Di Matteo's reign, and (as always) they do an excellent job illustrating the changes.
Largely because of this, most fans are assuming that we'll be seeing a very basic 4-2-3-1 for most of this coming season. They're also judging many of our rumored transfer targets based on how they'd fit in that 4-2-3-1. While this would make some sense, it's certainly worth noting that Di Matteo has never come out and said anything about the basic formation he's planning on implementing next season. It's also worth noting that neither of the Champions League semifinals against Barcelona (leg 1, leg 2) or the final against Bayern Munich featured what most would describe as a 4-2-3-1. It seems a bit odd to me that we're all assuming we'll be a 4-2-3-1 team when we didn't use that formation in any of our 3 biggest games last season.
What's also interesting is looking at the attacking options in Di Matteo's squad when he took over. Daniel Sturridge and Fernando Torres were in an awful runs of form when AVB was sacked. Juan Mata was pretty clearly exhausted and suffering from being overworked. Didier Drogba was still dependable, but we just weren't seeing him play well when he was starting every match. Romelu Lukaku and Salomon Kalou did not exist. Florent Malouda had clearly proven he offered nothing anymore. Nicolas Anelka was in China. One of the only real attacking positives when Di Matteo took over was the fact that Ramires was having a breakout year and demonstrating that he could realistically play a more advanced role than he had in the past. It's hard to picture Di Matteo having any options other than what he did with such an underwhelming attacking "force" at his disposal.
Now let's take a look at this transfer window. We've added Eden Hazard and Marko Marin. Gael Kakuta and Kevin De Bruyne are getting a shot at the first team in training. We've definitely bid on Andre Schurrle, Victor Moses, and Oscar after already signing Marin and Hazard. There is lots of chatter linking us to Hulk and Willian. We really haven't heard much in the way of concrete links to anyone who we'd expect to step right into the deeper midfield roles. The right backs we've been linked to thus far are all guys noted for covering large amount of ground and getting forward into the attack.
So what do these signings and rumors say to me? They're telling me not to be surprised if we don't look to be playing a 4-2-3-1 for the start of the season, but instead have something much closer to the 4-3-3 that we ran under basically every other manager we've had since Roman took over. That 4-3-3 system pushes the wings further forward, something that seems to ideally suit the players we've added and are targeting. It leaves a number of natural roles for Ramires, as most 4-3-3 systems rely on more of a lone holder than a double pivot. It would require fullbacks that can cover more ground than Jose Bosingwa ever did. It wouldn't require a "deep lying playmaker" (which we don't seem to be targeting anyway) the way our 4-2-3-1 did.
It's entirely possible that Chelsea open the season playing primarily the 4-2-3-1 formation that we saw in league games last season under Di Matteo. It's also equally possible that we plan on playing a 4-3-3. I wouldn't rule out a 4-3-2-1 or 4-2-1-3 either, as we already have the personnel to implement either of those without much trouble. The bottom line is that we really have no reason to assume we're strictly a 4-2-3-1 team next year, and we have plenty of reasons to believe we won't be. After all, nothing Roberto Di Matteo has done at Chelsea should indicate that he won't alter his tactics dramatically if he thinks it's in the club's best interest. We'll have plenty to watch for on Wednesday, but looking closely at how we approach Sounders FC from a tactical standpoint will be right at the top of that list.
Related: An alternate formation to consider / Follow We Ain't Got No History on Twitter