Theo Walcott believes Arsenal's players lack faith in their own ability and has urged his team-mates to express themselves and "show more commitment" as they seek to haul back fourth-placed Tottenham Hotspur this week.

Arsenal are seven points behind Spurs, who currently occupy the final Champions League qualifying place, as they prepare to welcome West Ham United to the Emirates Stadium on Wednesday . Having seen his side's second-half revival against Chelsea on Sunday fail to get any reward, Arsène Wenger admitted successive losses first to Manchester City and then at Stamford Bridge had damaged the club's prospects of reaching Europe's elite competition for a 16th year in succession, and pointed to a "psychological" issue within the side which has contributed to sloppy starts in both those contests.

Those sentiments were echoed by Walcott only days after the England forward agreed a new three-and-a-half-year contract worth £100,000-a-week to become the highest-paid player at the club. "I think there's a lack of belief as to how good we can be," said the 23-year-old, whose consolation at Chelsea was his ninth league goal of a productive season. "We've got some very, very good players here. I think players don't believe they are good enough at times. But, trust me, I see them every day in training and they should believe that.

"We've got a great bunch here, a great manager and he always puts it upon himself which is hard because we are the players out there every week. We try to win for him: we need to win for him because he's been very helpful for us young players coming through. We need to start realising how good we are. We showed some great stuff in the second half at Chelsea, but it's time we did that from the start. In that first half we were too slow, too sloppy closing down and we've got to show more commitment.

"We gave Chelsea too much space as well. As soon as we pressurised them a bit more, pushed up higher, we caused them problems. The manager said if we got that early goal then it would be different. It wasn't meant to be, but we gave the manager something to think about and we can't be slow off the blocks like that again."

Nerves have appeared to grip at the start of both those high-profile recent games, even if Arsenal were reduced to 10 men early against City and both Chelsea goals on Sunday were controversial, with that lack of focus infuriating the management. Wenger suggested his side were poorly positioned, "stretched" and not tight enough to discomfort the hosts at Stamford Bridge, "allowing them to play wherever they wanted". "There's a psychological part to it, for sure, because we didn't really go for it at the start again," he said. "In the big games, once you start 2-0 down, it's very difficult."

The manager can at least take solace in the reality his side's next three league games are all at home, given they have won only twice in 11 away games in all competitions since October. Victory over West Ham would trim the gap to Spurs to four points – the sides meet at White Hart Lane on 3 March – with Walcott insistent Arsenal can still repeat last season's feat to haul in their rivals and secure qualification for the Champions League.

"Last year, we were so many points behind no one ever thought we would make it," he said. "We've got a game in hand but we need to clock up these points fast. The gap doesn't worry us. We hope they do drop points. But we've got to concentrate on ourselves, win games and we've got a big game on Wednesday when we have to pick ourselves up. We are ready, it's our game in hand, we have to get three points and, no disrespect to West Ham, we should win that game."