Fabianski, 21, looked assured and saved a second half penalty to deny Partizan the chance to mount a comeback in the Gunners' 3-1 Champions League win on Tuesday night.
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"Fabianski had a good game, we have seen the player who we see in training," Wenger told reporters.
"He had a faultless game. I know it is in him. He got it out in the game and hopefully that will give him the needed belief and confidence.
"I am confident he will come out as a great keeper, I have always said that. We have to keep confidence in him and he needs to gain experience from games like this."
However, Wenger refused to confirm whether Fabianski, who came in for Manuel Almunia who has an elbow injury, would be picked as the last line of defence at Chelsea on Sunday.
"At the moment Almunia is injured, we will have to see how his injury goes, but at the moment it is too early to say."
The Arsenal boss was also pleased with the contribution of Marouane Chamakh.
"He’s a good player who fights very hard and he gets important goals and that’s what you want from your strikers.
"We have great strikers at home who are injured and last year we missed them for a while so we had to add somebody and he is a good addition."
By Luke Nicholls
