A much-changed Gunners side - without rested key man Cesc Fabregas - were unable to breakdown the hosts, who had let in seven at Emirates Stadium a fortnight ago.
"The result is quite positive because we qualified and did not concede. We came here to qualify," he said. "The defensive performance was good, but the offensive performance was average."
The Arsenal manager added: "The conditions were difficult and Slavia defended very well. They felt humiliated after the 7-0 and were determined not to conceded. Our tempo was not high enough to create space for chances.
"We are through and can play better than tonight, but the overall performance of the team has been outstanding."
Wenger refused to blame the drop in performance on his rookies.
"I would not like to blame the youngsters tonight because it was very difficult to find our game," he said. "I am convinced they have learned it is difficult away from home in the Champions League and they will do better in the next games."
Wenger said: "We have two games to go, we are qualified so I might continue to rotate if I feel it is needed."
He added: "To finish top is important.
"The second game is at home, and you play the team second in another group, so it is a double advantage."