I think we are suffering from many issues, and there isn't one single one that's the most defining. But I'm most interested in the tactical part of the game, so I'll go from that angle.
It's been abundantly clear to everybody I think, that our extreme narrowness in attack is backfiring against us. This is most often what our attack looks like in terms of shape when Fabregas picks up the ball in possession:
http://lineupbuilder.com/?sk=9by7d
While that doesn't look so bad at first glance, it's important to know that because our attacking 3 are so narrow, teams can congest the middle of the pitch with lots of numbers and close down the passing lanes, making Fabregas play a sideways or back pass. And since opposition are dedicating so many numbers in the centre of the park basically daring us to attack down a wing, they can press our midfield players often Matic and Fabregas on the ball. Matic will always play the safe pass, but that will eventually lead to the same cycle being rinsed and repeated, and Fabregas has been caught in possession a lot this year, and given the ball away high up in midfield, which leads to quick transitions and counter attack possibilities.
I actually don't think our defense is as tragic as everybody thinks it is. Everybody looks and sees 22 goals conceded in 11 matches and goes, jeez, our defense is terrible. But there have also been a fair amount of goals where people turn around and say wow we have no luck. And naturally people ask, how much of our goals conceding is bad defense or just dumb luck. And well, using Michael Caley's widely applauded expected goals formula, it's more the latter. We have conceded 22 goals, but only 11.8 expected goals allowed, by far the biggest differential in the PL between actual goals allowed and expected goals allowed. A lot of that is luck, and a lot of that means teams are converting some ridiculous chances against us that have an extremely low probability of scoring, as well as taking the chances they do get very well. We are 7th in expected goals allowed in the PL despite allowing the 2nd most goals, which leads me to believe that we are due for a run of clean sheets.
The area I'd be more concerned with is expected goals, which, even though we have scored 16 this year, we only have 12.2 expected goals, which is largely due to the fact that we have hardly scored any goals from open play, and goals like Willian's free kicks have a low expected value due to how freaking hard it is to score from them even though he makes it look easy.
TL;DR The narrowness in attack is hurting us in our attack and defense, but our defensive woes are vastly overstated and the expected goal #'s (9th in expected goals, 7th in expected goals allowed) leads me to believe we'll do better over the course of the season than we are doing at the present time.
For anybody who's interested about expected goals and some other stats like that about Chelsea and the rest of the Premier League, here's a great link:
http://cartilagefreecaptain.sbnation...hot-statistics <-- read the glossary first at the bottom to help understand the stats!
