transfer deadline day.
Arsenal are unbeaten in 10 games in all competitions and the Germany playmaker was central to the Gunners' 2-0 win over Napoli in the Champions League on Tuesday, scoring his first goal for the club.
"He enjoys playing football, he enjoys playing with his partners," said Wenger. "Of course he has given everyone at the club a lift and belief, and belief is a part of the success of football."
Liverpool, two points behind the leaders, host struggling Crystal Palace on Saturday boosted by last weekend's goalscoring return of striker Luis Suarez against Sunderland after a 10-match ban for biting Chelsea's Branislav Ivanovic.
"He's just given us more confidence," team mate Lucas Leiva told the club website (www.liverpoolfc.com).
"The squad that we had without him was a good one, but with him back in it, we'll be even better. He's one of the best in the world."
Seventh-placed Manchester City, who have yet to win in the league away from home after losing 3-2 at Aston Villa last time out, return to the Etihad Stadium to face Everton on Saturday.
City will be looking to rebound after suffering a humbling 3-1 defeat at home to Bayern Munich on Wednesday as last season's Champions League winners handed out a masterclass in possession football.
Chelsea travel to Norwich City on Sunday without striker Fernando Torres, who was already suspended for the match but limped off with a knee injury during the 4-0 win over Steaua Bucharest in the Champions League midweek, and Tottenham Hotspur, in third, take on London rivals West Ham United.