Hugo Lloris says Tottenham "cannot be in a worse situation" ahead of Sunday's north London derby with Arsenal at Emirates Stadium.
Spurs were beaten 1-0 at Wembley by Bayer Leverkusen on Wednesday, leaving their Champions League hopes hanging in the balance.
Mauricio Pochettino's side is third in Group E on four points, two behind Leverkusen and four adrift of Monaco, which it visits on the next match day before hosting CSKA Moscow.
Although unbeaten in the Premier League with five wins and five draws this season, Spurs have not won any of their last six in all competitions - a worrying sequence for Lloris ahead of a crunch derby.
"We cannot be in a worse situation. It is difficult to accept that kind of performance from us," he said following the Leverkusen loss. "It was difficult to recognise the team, very aggressive, very calm under pressure, and that was completely the opposite.
"We need to learn quickly because there is a big game on Sunday. The derby is always important and we need to forget about this disappointment and be ready."
Spurs have been struggling with injuries of late, with Harry Kane, Toby Alderweireld, Mousa Dembele, Erik Lamela and Danny Rose all suffering, but Lloris is making no excuses for their winless run.
"We cannot depend on one, two or three players. We need to think as a team," he said. "In football there are ups and downs. It is difficult because this game was very important and I did not feel we were aware of that. Leverkusen did not play a great game. They were just well-organized and had some chances because of us, because we made too many mistakes.
"It is true that maybe we lost a bit of confidence because it is a few games we have not won. We have to keep working and be ready for the big game on Sunday."