The Blues approached yesterday's game at Stamford Bridge as clear favourites, but they finished empty-handed after being stunned by goals from Andre Santos and Theo Walcott and a hat-trick from Robin van Persie.

The second-half attacking display from Wenger's men was vintage Arsenal - a performance full of speed, creativity and ruthless finishing that hauled the north London club to seventh in the Barclays Premier League.

The performance was a far cry from their displays in the opening stages of the season when, fresh from the departure of Cesc Fabregas and Samir Nasri, Wenger's new-look team lost three of their opening four games - one of which was an 8-2 humiliation at Old Trafford.

The 62-year-old has since guided the club to eight wins from nine matches after the new members of his squad finally began to settle in.

Wenger feels the likes of Gervinho, Per Mertesacker and Mikel Arteta have started to gel with the rest of the Arsenal squad - an opinion based on the united celebration the away side performed in front of their travelling support following yesterday's lunchtime's morale-boosting win.

The Frenchman, whose side play Marseille on Tuesday, is glad that to see that his men have put their rotten start to bed.

"If you have gone through what we have gone through since the start of the season, it's reassuring for me," Wenger said.

"The players have suffered, but that shows the belief and spirit is back.

"The spirit is great and all this together explains why the players reacted like that (after the final whistle).

"The spirit is strong and you feel that in the dressing room.

"The players are determined together and they want to play like we did against Chelsea. That encourages us to believe that we have the quality."

Arsenal's upturn in form has been largely down to the form of captain Van Persie.

The striker tapped home Gervinho's pass to score Arsenal's first yesterday before he wrapped up the win with two goals towards the end after Chelsea had pulled the score back to 3-3 in a thrilling game in west London.

Van Persie has scored 12 goals for his club this season - a remarkable achievement which Wenger was quick to hail yesterday.

"He has exceptional class. He has scored 27 goals in 26 games in 2011," the Frenchman said.

"There are many factors why he is in such good form. He has experience, he is top quality and he's at the right age as well.

"When you get to 27 or 28 you start to analyse quickly the weaknesses of the defenders around you, and you know how to take advantage of them and you also know how to take advantage of your team-mates around you."

Van Persie is 28, and Wenger said: "His intelligence of movement is exceptional and his confidence at the moment is so high that he takes advantage of every situation.

"The captaincy has contributed to his form as well."

Despite Van Persie's heroics, and a wonder strike from Juan Mata that levelled the scores at 3-3 with 10 minutes left, the goal of the game came from Walcott.

With England manager Fabio Capello watching from the stands, the winger picked himself up after slipping in a challenge and burst past three more Chelsea players with exceptionally quick feet before slotting past Petr Cech.

Walcott has come under fire from some sections of the Arsenal support at times this season for his performances, but Wenger thinks the former Southampton winger is now back to his best.

"He has been struggling for us because we make him work very hard and I believe that he has become a more complete player," Wenger said.

"He is not a liability any more defensively. He does his defensive job.

"At the start he got heavy legs when he went to win the ball back but now he is getting used to it. He does the job defensively and he is still dangerous going forward."