The 26-year-old has come under fire in recent weeks after committing errors that led to goals for Southampton, CSKA Moscow, and at Newcastle United last time out.
When asked by Sky Sports News about the Germany international, Wenger said: "His confidence is lower. He has played many games and most of the mistakes he made have been post-Europa League games because he was a bit jaded.
"On that front that is part of the fatigue factor which would be the explanation why he had some less good games. We are in a job where we can't demand that people, when you make mistakes, say that it's absolutely wonderful. That's part of Arsenal. Like me when I lose games, I have to accept that.
"He is a young defender who has had ups and downs. I believe overall he has potential. He is one of the guys who is committed and goes for the challenges. He is not one guy who hides from the responsibility, so overall he will be a promising defender for the future. Experience helps."
Mustafi joined Arsenal for a fee in excess of £30m in 2016.