It's been a very shaky period for Chelsea of late and a lot of people are asking why.
As a central defender myself, I always look at the players in the heart of the back four because if you're rock-solid in that area it doesn't matter what's going on around you. If the centre-halves are standing firm then clean sheets and positive results generally follow.
It's no surprise that Chelsea's loss of form has coincided with dramatic changes in the central defensive positions. Injuries to John Terry and Alex have resulted in Carlo Ancelotti choosing a number of different combinations in that area and that doesn't breed confidence.
People talk about the absence of Frank Lampard or Michael Essien, but I think that the defensive positions are more important. Essien was back in the side on Saturday and they still couldn't beat Everton at home.
I know Terry returned alongside Branislav Ivanovic, but Alex was missing and they just can't find any consistency in that position. We've seen Terry, Alex, Ivanovic and even Paulo Ferreira all play there this season and there is a lack of quality cover. I would argue that Tottenham probably have more strength in depth than Chelsea do at the moment.
They are really missing Ricardo Carvalho, a quality defender who knows the position inside out. They have been very light in that department since his departure and it's an area that Ancelotti may need to address in January.
I've never seen Ancelotti stand up during games as much as he has done in the last few fixtures.
When Ray Wilkins was alongside him he would spend most of the game discussing matters on the bench and I am starting to wonder if the issues off the field are starting to have an impact on the manager.
As I have said on Soccer Saturday, you cannot underestimate the significance of a trustworthy number two. It needs to be somebody you have chosen, rather than somebody who has been put there by the club - and I think it was wrong for Chelsea to push Wilkins out of the door, especially in the middle of the season.
Arguably Chelsea had an easy start to the season compared to the other title contenders and a lot of people said they were doing well when they put a string of wins together. However, people within the game realised they hadn't come across any big teams yet and in the last few weeks they have been found wanting.
Their next three league games are against Tottenham, Manchester United and Arsenal and they need to step up for those fixtures or else they're going to find themselves adrift.
Before that they head to Marseille for their final Champions League group game and although there is nothing riding on it, Ancelotti desperately needs a win to boost his team's confidence for those big Premier League games.
So I don't think they'll take this lightly - and Didier Drogba certainly won't. He is very passionate about the French club following his time there and he will be looking forward to playing in this game.
I think Ancelotti will rest a few players, but a morale-boosting victory will be the order of the day.
THOMMO'S VERDICT: I see Chelsea winning the game, but it will be a very, very narrow victory. I can see Marseille scoring, so I'll go for a 2-1 win for Chelsea ahead of a very important few weeks for them.