Wenger saw the 19-year-old score on his Arsenal debut last season and knows he will pose a threat.
"Sanchez Watt is a player who is left-footed, talented, good on the ball and a good dribbler," the Frenchman told arsenal.com.
"He will certainly put every effort in and I hope he will not play tomorrow."
Wenger's tongue was partly in his cheek for that final remark. The Arsenal manager wants the teenager to do well and has always defended the right of loan players to line up against their parent club.
"I always said that when you give the player on loan it was a bit unfair not to let him play against you, because it gives an advantage to the other clubs," he said.
"I had the case many times, and always gave permission for the players to play. Before in the Premiership, you could give permission for the player to play, and I always did.
"When you give a player out on loan, you cannot forbid him to play against you."