There is obviously no easy way to answer this question but I will try to nonetheless. Numerous people have asked me whats wrong with Chelsea this season. 4 points from four games suggests there is more than one factor contributing to this phenomenon. Below are the various factors that, I believe, have lead to a below par Chelsea so far this season.
From the title you might assume I am referring to Chelsea's preseason form, something people generally don't like reading too much into, but I'm not. Late last season, Mourinho and his staff decided that player fatigue due to his minimal rotation policy, and not competition, was the number one threat to his side retaining the title. They believed that had Chelsea players not been as tired as they were towards the end of the 2014/15 season that Chelsea would have won the league even earlier than they did and with a great points total. Mourinho and his staff then decided that they should give the whole team an entire month off for the summer. This is an entire week later than any other premier league side. Chelsea taking this risk is supported by the fact that Mourinho thinks his team last season were ready to start the season a week early and as a result it would be okay to start preseason a week later. It was hoped that his decision might help various players that have been suffering from playing "too much football" over the last few years (Hazard, Ivanovic, Oscar etc.). While that might be true, this calculated risk has SEVERELY backfired. Not only do the players look sluggish, the look under prepared. The football has been reminiscent of the Scolari days, not in the style of football played but in the players genuinely looking clueless when in possession. Passes around the box aimlessly and backwards in a lack of ideas have happened far too often in Chelsea's opening fixtures, something that hasn't really happened at any point during Mourinho's second tenure or, indeed, the first.
Obviously it goes without saying that under-performing players are part and parcel of the game and that any manager should know how to deal with this issue when it arises. However, the reason this is key with Chelsea at the momoent is because it has been happening with key players in the Chelsea side and most notably in Chelsea's back 6 outfield players. Ivanovic has looked like a League 1 Right Back playing in the Premier League. Terry has looked exposed. Cahill looks panicky. Matic's foul count per game is double his average from last year (a key indicator for the performance of a DM) and Fabregas' performances can only be described as casual. A lot of fans tend to analyze Chelsea's backline individually and talk about how good or bad each are as players. In recent years I've heard things such as "Terry is too slow", "Cahill is reckless" and the sorts. But these points are completely irrelevant when it comes to Chelsea because (although it is cliche to say) Chelsea's defense performs as a single unit. They function as a unit and all 6 players move and deal with the threat accordingly.Testament to this is the fact that we rarely see a player run at Terry directly or run at the heart of the defense unchallenged. In every single one of the Chelsea games so far, the incorrect positioning and general under-performance of numerous players in the defense have meant we have seen far too many players run at the Chelsea backline unchallenged thereby exposing their individual weaknesses. Basically, because various players in the unit are not doing their job, the weaknesses of each player (e.g. Terry's pace) are exposed and capitalized on. Nine goals conceded in the first four league games is Chelsea's worst in nearly 40 years.
Fabregas importance in the functioning of the side is so crucial it deserves a note in itself. The main difference between the 13/14 season (where Mourinho famously used the small horse analogy to describe his Chelsea side as not ready to compete) and the 14/15 season was not only the addition of a proven goalscorer in Costa, but also the addition of Fabregas. The ability to quickly and decisively turn defense into attack was a crucial characteristic Mourinho's Chelsea side was lacking and a deep play maker such as Fabregas was the perfect solution. If teams didn't mark Fabregas, he would provide the forward players with pin point passes and find their runs behind the defense. If they did mark him, the gaps left in the midfield or the wings as a result would prove to be very useful for the Attack Mid trio (Hazard loves having a bit of space to run into). However, an under performing Fabregas that is seemingly incapable of doing his job and thereby does not need to be marked leaves Chelsea where? It leaves Chelsea in exactly the same predicament they were in the 13/14 season, a team without the ability to break down a good defensive unit - A characteristic crucial in any side with aspirations to compete for the title.
Lack of competition
Although Mourinho has repeatedly recognized that a number of his players throughout the entire team an not just the backline have been underperforming, he has repeatedly selected them to play in the next match. One can only assume that it's because he does not have the ability to make any other decision. This is particluarly true with the defensive line. The departure of players like Felipe Luiz and Cech who were more than capable players to be rotated with the side has meant Mourinho's side now more or less picks itself. Obviously these players have been replaced and the side has been beefed up as a whole but the additions were done so late in the day that they are not yet ready to be integrated into the squad. Being forced to keep picking underperforming players is something no manager likes to do and cannot be good for the side overall. Ironic that the depth of the squad last year was not needed last year, but this year.