Roberto Di Matteo admits Chelsea's attempt to qualify for the Champions League will be over if they lose their crunch clash against Tottenham Hotspur on Saturday.
Chelsea have never failed to qualify for Europe's elite club competition during owner Roman Abramovich's reign, but Di Matteo's side slipped five points behind fourth-placed Spurs after Wednesday's 2-1 defeat at Manchester City.
The Blues' interim boss knows a loss to their London rivals at Stamford Bridge this weekend would leave them with virtually no chance of making the top four.
"Obviously, a win would give us a big, big lift. But, also, if we manage just to get a draw, I think we're still in it. If we lose, I think it will be very difficult afterwards," he said on Friday.
"Mathematically it is still possible so we will fight until the end but we are looking to have a good game on Saturday."
Di Matteo believes Chelsea's hopes of finishing in the top four are already in danger because they have a much tougher fixture list than Tottenham and third-placed Arsenal.
"Certainly, we have the most difficult schedule and fixture list until the end of the season compared to the other teams," he said.
"But we have a good team, we have a good squad, almost fully fit squad as well. We have all the resources that we need to be able to challenge for that."
At least Di Matteo can welcome back captain John Terry after the England defender missed his club's last two matches with calf cramps.
Di Matteo expects Terry's experience and leadership qualities will be major assets in such a vital match.
"He's very influential for us in the team and we are very pleased that he's back," he said.