Arsenal must solve their defensive frailties from within if they are going to challenge for a top-four finish in the Premier League this season, says Arsene Wenger.
The Gunners have slipped eight points off the Champions League qualification places after one win in their last five league games.
Tuesday's 3-1 defeat to struggling Swansea City only highlighted Arsenal's problems at the back further - mistakes from Nacho Monreal and Petr Cech gifting the Swans victory.
Wenger branded the performance "very poor" with "no rational explanation" for the goals they conceded at the Liberty Stadium.
Arsenal tried to bring in Jonny Evans on deadline day to provide a further option in defence but that bid failed, leaving Wenger to challenge his side to improve.
"It has been a [rollercoaster], we lost a game we should not have lost," Wenger told a media conference ahead of Saturday's match with Everton.
Although mistakes are part of the game I always expect 100 % from myself and I'm not happy with the one I made today ... back to work tomorrow !-- Petr Cech (@PetrCech) January 30, 2018
"January has been a very difficult month for us, it has been disappointing on the pitch, we have no room for any more defeats, it is important we respond quickly.
"I believe we have to find an internal solution to our defensive problems, that's everyone putting more effort in.
"It is not a lack of effort, but a lack of focus in vital moments of games, sometimes we do it well, sometimes not.
"At Swansea we had 75 per cent possession, but we forgot to defend when we lost the ball.
"It's a team problem, and it is about taking individual responsibility for defensive roles."