Arsène Wenger said his team cannot afford to drop any more points if they are to secure Champions League qualification for a 16th consecutive season, with the Arsenal manager left to reflect on a "damaging week" after defeats to Manchester City and Chelsea.

The loss at Stamford Bridge left Arsenal seven points behind Tottenham Hotspur in fourth place, although they have a game in hand which they will play against West Ham on Wednesday. While the gap above Arsenal is bridgeable, Wenger is worried about psychological weaknesses in his side that have left them playing catch-up in games against other contenders.

"We have lost two big games in the last week and that's very damaging for us," he said. "We cannot afford to drop points any more if we want to be in the top four. This was very similar to last week. The team has fantastic quality and spirit but we only come into the game when we're 2-0 down. At the moment, that's worrying. In the big games, once you start 2-0 down, it's very difficult.

"Chelsea played well at the start but we were not well positioned on the pitch and were stretched, giving them too much room to play. We didn't defend tight enough and allowed them to play where they wanted. There's a psychological part of it, for sure, because we didn't really go for it at the start again.The team have to believe more in the quality we have."

Wenger had justifiable complaints over both goals, with Ramires's foul on Francis Coquelin going unnoticed ahead of Juan Mata's opener and the Brazilian tumbling eagerly over Wojciech Szczesny's challenge to earn a penalty moments later. "The referee gave a lot of free-kicks and some for much less than the Coquelin one," he said.

"It's frustrating. It doesn't mean we should have conceded the goal but in the big games these decisions have big implications. It wasn't a penalty, and he could have given Ramires a yellow card [for diving] as well. But we didn't make enough of our corners, free-kicks and the chances we created. That's why we lost the game. It's very damaging for our position in the league and difficult to swallow."

This was only the second home win in seven domestic matches for Rafael Benítez to celebrate, with victory building on the upbeat mood generated by confirmation that Ashley Cole will sign a one-year extension to his £120,000-a-week contract . "We're really pleased," said the Chelsea interim manager, who had been denied David Luiz due to an ankle injury. "When you are in the top four and want to stay there, Arsenal are one of the biggest rivals. Everyone worked hard, we controlled the game, created a lot of chances and deserved to win."