Walcott scored in the Gunners’ 2-1 win at Marseille in September, but missed the subsequent 12 matches with an abdominal injury, which required minor surgery.
However, Wenger is set to include Walcott in his squad when the Premier League leaders welcome third-placed Saints to the Emirates Stadium, hoping his direct approach can unlock the division’s meanest defence.
“Theo has not played for a long time, he has not played even a reserve team game, but I will put him in the squad on Saturday,” said Wenger.
“Of course you miss a player like Theo Walcott. Strikers who get behind the defenders have a very important quality and Theo has that quality.
“He can always give you a different option in the game and that is of course vital. Theo has different qualities to other players and I am very pleased that he’s back.”
Southampton manager Mauricio Pochettino, however, has warned his players the greatest threat to their proud record of five goals conceded in 11 league games so far this term will be creative midfield duo Mesut Ozil and Santi Cazorla.
“I rate Mesut Ozil as one of the top 10 players in the world,” he said.
“It is clear they are two great football players. It is clear that you cannot afford to grant them any space or time to think because they are players with individual actions who can decide a game on their own.”
The condition of midfielder Tomas Rosicky will be assessed today before Wenger finalises his team, though Lukas Podolski and Alex Oxlade-Chamberlain remain out.
However, Jack Wilshere, who has been dogged by an ankle injury this term, is fit to play having come through both of England’s friendly defeats to Chile and Germany at Wembley unscathed.