Which is why you should expect much more from him. His first couple of matches were alright, but it's been a while now since he's had a good game, and he's yet to show anything truly outstanding.
I know it's his first season in England, which takes some getting used for certain players, but a player of his caliber should still be able to show more and have a more immediate impact on the pitch.
His transfer has definitely had an positive effect on the club (mentally and play-wise), but I think that effect will completely start to die out after today.
His performance today was abysmal at best, worst player on the field. Lost the ball on a number of occasions, which cost us a couple of goals, and he didn't do any running back or defensive work after having lost the ball. That seriously pissed me off, he seemed completely uninterested and lazy. He'll end up being a new Arshavin, if this attitude continues.
Wenger also has to take some blame, he completely fails to motivate the players for certain games, and at times it seems they are not even properly prepared when the game starts.
(sorry, I feel kind of angry after having watched that match, I might be a bit overly dramatic right now)