During his post-match interview, a dismayed Antonio Conte said "This is the fourth defeat in 16 games".
While it was a famous win for West Ham over their London rivals, it was a body blow to Chelsea's hopes of retaining the title as they were already trailing Manchester City by eleven points ahead of the weekend. But Conte has stopped short of criticising the player, even claiming that he had a good game against West Ham.
After the champions lost 1-0 at relegation-threatened West Ham, Conte blamed fatigue in his players and what he considers a thin squad for the club's demise from top spot.
"He satisfied me with his performance".
"Our start was bad but today we played a bit exhausted".
Then at 1-0 down, we tried but you have to know in this situation when you play against West Ham in a London derby, it is very hard.
"It means you are not in the title race".
"We have to fight and do our best". "[At the start of the season] I said it well be very tough, very hard". "We started our pre-season with the same players; a lot are always playing, and for sure you have to pay something for this".
It is obviously not impossible to compete in the Premier League and the Champions League, but what is definitely clear is that you need a squad full of quality and depth to compete in both competitions simultaneously.
"The final decision [on transfers] is the club".
"I don't want to speak about this", he said, "we have just started December and there is one month before January".
"We got a big boost from the performance at Manchester City, that was something we could talk about positively, and we do have the players to threaten in attack once we get the back end sorted out", he said.