The England international has been sidelined for two months after he sustained an abdominal injury in September.
"He is one of the players who goes behind (the defence) without the ball," Wenger told Arsenal Player. "Strikers who get behind the defenders is a very important quality and Theo has that quality.
Arsenal are 7/2 with William Hill to win the Premier League this season
"Of course you miss a player like Theo Walcott. Theo had a good start to the season, he scored goals, he provided chances and had assists. He can always give you a different option in the game and that is of course vital.
"You always want to have a perfect balance (in attack). If you look at our results our balance was not too bad.
"But Theo has different qualities to other players and I am very pleased that he's back."
Should Walcott return to action on Saturday at the Emirates Stadium, he will be coming up against the side with which he started his professional career.