"But since he has joined the club he's made a big impact and I've been very pleased with him. You can see he is a winner and you want that in your team."
Lehmann takes over in goal tomorrow when Arsenal meet Middlesbrough in an FA Cup fourth-round tie. He was rested for the 1-0 defeat against Boro in the first leg of the Carling Cup semi-final on Tuesday.
Although the line-up will be stronger than in midweek, there will be no Thierry Henry as he takes what Wenger has called a "much-needed break" after a hectic first half to the season. Dennis Bergkamp is in line for a return with either Freddie Ljungberg or Robert Pires pushed forward from midfield. Sylvain Wiltord and Jeremie Aliadiere are both injured while Kanu is on African Nations Cup duty.
Tomorrow's clash is the third of four scheduled meetings this month between the sides and Wenger does not want there to be a number five.
Wenger added: "I don't want a replay but I still want to win the FA Cup. So if we get a last-minute equaliser I'll be happy."