Right now, we don't know how serious Michael Essien's knee injury is. Chelsea have confirmed there's a problem but they also don't know how bad it is, and won't for a couple of days. From that news, we can infer that there's enough swelling that the injury isn't particularly minor, but we don't know if the Bison will be out for one month or twelve. Any guess is just that, a guess.
But that doesn't stop us exploring possible repercussions of the injury. The short term, where Essien is back for the start of the season, isn't going to be a major problem, but there are a couple of scenarios in which the injury has a major effect of what Chelsea do in the transfer window and how Andre Villas-Boas sets up his squad. Let's take a look.
Michael Essien has suffered a minor ligament sprain and will be out until early August. He'll miss all of preseason and thus won't be available to start the first few games of the season as he builds up the match fitness he couldn't work towards over the summer. Chelsea do not change transfer targets or strategy, field him on the bench for the first three games with Ramires starting, and thereafter let the two compete for the box to box midfield role.
Impact: Negligible on all counts. Essien rested more throughout 2011/12 season.
Partial Ligament Tear
Michael Essien has suffered a partial tear of the anterior cruciate ligament (ACL) in his right knee and will be out until the beginning of December, missing key games against Manchester United, Arsenal and Liverpool. He is expected to return to the squad for the December 10th home game against Manchester City, depending on how his rehab goes. Chelsea change transfer policy to protect defensive midfield depth, taking John Obi Mikel off the market and putting even more weight on finding a replacement midfielder. The price of both Luka Modric and Javier Pastore goes up by £5M.
Impact: Medium in terms of on-field play, severe restrictions in Andre Villas-Boas' transfer flexibility.
Full Ligament Tear
Michael Essien has suffered a complete ACL tear in his right knee and will be out for much of the season, probably recovering in time to contribute to the run-in a la Yossi Benayoun last year. His left knee is operated on simultaneously to clear up lingering problems from ACL and medial cruciate injuries suffered over the past few seasons that have never fully healed. Although there are whispers that the injury could have a major impact on his career, there's some hope that the time taken to fix both knees could prove beneficial in the long run.
Ramires assumes the primary box-to-box role, but David Luiz is pushed into the central midfield as well to act as backup for both his Brazilian teammate and Mikel. Chelsea look hard for cover at centre back in both the summer and winter transfer windows and make a very strong push for a long term replacement for Essien, with FC Porto's Joao Moutinho on the list, although he's not expected to be quite the all-rounder Essien is. Club has difficulty pursuing non-midfield targets, although continues to chase the likes of Luka Modric and Javier Pastore.
Impact: Major on-field problems which require other players to step into unfamiliar roles; major impact on Chelsea's summer and winter transfer policies; unknown effect on Essien's career - could be restorative or extremely detrimental.
Of course, that all ignores the emotional cost to this injury (to us, not him, although I imagine he's pretty down about life right now. I wish I could send him a bucket full of hugs). Essien is a fan favourite, and for good reason - in his time with Chelsea he's been the key to an absolutely dominating midfield. When he's gone, the team misses him dearly, and the fans do too. He's seemingly one of the unluckiest men alive in terms of knee injuries, and it'd be a real shame for football if this was severe enough to put him out of action for a significant amount of time.
As far as impact to Chelsea is concerned, we'll have to wait and see how the results come out. This could all turn out ok, or it could be very, very bad.
PS: Essien picked up his first major knee injury within days of me buying his personalised jersey. The past few years have been my fault. I'm really sorry, Michael. :-(