Arsene Wenger has admitted that he is concerned by Arsenal's performances against their leading rivals as fears grow that they cannot compete with the Premier League elite.
The manager said on Tuesday that his players' morale was severely affected by their 2-1 defeat by Chelsea on Sunday, which left them 22 points behind Manchester United, the leaders, before on Wednesday night's match against West Ham at Emirates Stadium.
That loss, coupled with Arsenal's 2-0 defeat by Manchester City in front of their own fans seven days earlier, means that Wenger is in real danger of missing out on a sixteenth successive season in the Champions League.
"What is worrying is just that we do not win the big games," Wenger said. "At the moment we do not get the results we want. The difference in points mathematically is not dramatic, but the consistency of our performances within games is what is worrying."
Wenger's side have the chance to get within four points of the Champions League places by defeating West Ham in a fixture that had to be rearranged because of a London Underground strike on Boxing Day, but Arsenal have failed to win in their past three league games
"We are of course very disappointed because we put a lot of effort into these games but we missed the start of the game and therefore we came out with zero points," Wenger said.
"The position we are in now is a bit backs to the wall because we have to respond. I'm confident that we will but the team was very down after the Chelsea game."
Theo Walcott admitted that a lack of self-belief among the players contributed to the defeats by City and Chelsea as he acknowledged that they had let down Wenger with poor first-half performances in both games.
"There's a lack of belief as to how good we can be," he said. "We've got some very good players. They don't believe they are good enough at times."
Selling Van Persie to United brought in �24 million, but missing out on Champions League football next season could cost the club �35 million. Walcott, though, does not believe the squad lacks strength in depth, nor does he subscribe to the theory that the manager is struggling to motivate his players.