The 27-year-old made his first appearance of the season in the Gunners' 2-0 win over Bayern Munich on Wednesday, replacing Wojciech Szczesny.
"He played with authority. We know his talent and I'm very happy with his performance," Wenger told the club's official website.
"He has changed a lot, there has been a complete mental transformation in Lukasz's attitude. He is more vocal, has more authority and mentally he absorbs the pressure of the game much better.
"He has a huge talent, which we know all about. Sometimes to go out of the game for a while helps people to mature and think about their own game."
Arsenal face Swansea City at the Liberty Stadium in the Premier League on Sunday.