Roberto Di Matteo admits Chelsea's bid to finish in the Premier League's top four would be all but over if they lose to Tottenham in the early kick-off.
Di Matteo's number one priority as caretaker Blues boss is qualifying for next season's Champions League and, despite masterminding a remarkable turnaround in the club's fortunes since taking charge, he knows it could all be for nothing if Spurs win at Stamford Bridge.
Wednesday night's defeat at Manchester City saw Chelsea slip five points behind Spurs, who dropped to fourth place after drawing against Stoke.
Di Matteo acknowledged tomorrow's London derby is a game the Blues dare not lose.
He said: "A win would give us a big lift. But, 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. Mathematically, it is still possible, so we will fight until the end, but we are looking to have a good game (against Tottenham)."