Arsene Wenger believes Olivier Giroud's decisive contribution to Arsenal's vital 3-1 win over West Ham is a sign the France striker is back to his best in time to fire his side into the Champions League. Wenger's team climbed back above Everton into fourth place in the Premier League thanks to Giroud's inspired strike and a brace from Lukas Podolski at the Emirates Stadium on Tuesday. The Gunners had fallen behind to Matthew Jarvis's first half header, but Podolski equalised and Giroud then produced a brilliant first touch and lethal finish to put the hosts ahead soon after the break. Giroud's majestic piece of control was reminiscent of Arsenal legend Dennis Bergkamp at his best and Wenger hopes the forward's performance bodes well for the final four games of the season. Arsenal have no margin for error as they try to pip Everton in the race for a top-four finish and Wenger desperately needs a dominant period from Giroud, who had fallen out of favour with the Gunners manager earlier in the season after lurid reports about his private life contributed to a poor run of form. Wenger even decided to start raw youngster Yaya Sanogo ahead of Giroud in two of the club's most important games of the season -- the Champions League last 16 first leg tie against Bayern Munich and Saturday's FA Cup semi-final win over Wigan. But he said: "Olivier is a great guy with a great mentality. He has gone through a difficult period as you know. "I think it affected his confidence but you could see he is refreshed now. "At half-time he came in very down because he missed a chance, but he is mentally strong and made up for it. "It was a perfect first touch. You need that if you want to score. "What I like is he used his upper body to make some space and after that he still had to finish it." Giroud's goal was the highlight of a  much-needed comeback from Arsenal after a lethargic first half threatened to make a mockery of Wenger's selection gamble. Leaving the likes of Aaron Ramsey and Alex Oxlade-Chamberlain on the bench, Wenger fielded his oldest starting eleven in the Premier League since May 2003. Yet, despite that average age of 29 years 188 days, Arsenal were still going strong at the end and Wenger hopes they can replicate that desire and energy for the final four matches of the tense run-in. "It was a gamble. I said before the game that it was one of the oldest teams I've ever played at Arsenal but I trusted the experience. That experience helps when your back is against the wall," he said. Wenger remains hopeful about Arsenal's European challenge, but he acknowledged Everton remain in pole position as a draw or win at home to Crystal Palace on Wednesday takes them back above the Gunners into fourth. "It improves the confidence of the team and we have one advantage; the picture is very clear in front of us," said Wenger, who revealed Germany midfielder Mesut Ozil is set to return from injury at Hull on Sunday. "It doesn't depend just on us but if we win all our games there is a chance of course. "We know we need Everton to slip up and we have to win all our games. Lets not focus on Everton, we just have to concentrate on ourselves." West Ham manager Sam Allardyce was vexed his side failed to press home their advantage, with Jarvis's decision to stay on his feet when fouled by Bacary Sagna in the penalty area another source of frustration. "We shot ourselves in the foot with the first two goals," he said. "The facts are that referees don't give penalties when you stay on your feet. For honesty there is no reward. "You have to make the referee's mind up. You should go down if there is contact." Source: AFP