The South Korea international was impressive on the night.
Wenger told arsenal.com: "For me I am very pleased with his performance. He had a very, very good game. He has shown intelligence in his link play with others. The quality of his movement was exceptional and his finishing is absolutely fantastic. He has shown tonight that he is a very, very good player. He is ready to play in league games, yes.
"Compared to the player who played in the first match [against Shrewsbury] where he was a bit inhibited, tonight I felt he played with freedom and has showed what a good player he is."