The Reds are unbeaten in the league this season and go into the match six points clear of rivals City after 11 games played.
"Well we have seen in recent years that they are very tight games," Wenger told beIN Sports.
"I personally feel they could not afford to lose [Aymeric] Laporte, Manchester City.
"If you look at their results, they still play great football but they are a fractionally a bit more vulnerable defensively. And that could be a big handicap against Liverpool."