Wilshere returned from an ankle injury, before being substituted in the second half.
Wenger said: "He worked very hard. He has been in full training since Wednesday. Walcott has only been in full training since yesterday, we thought he had enough in the locker to play an hour.
"I maybe would not have put him straight away in if Rosicky was fit.
"I did not want to destructure the team who have been successful and he was the best for this position."