Arsenal sit five points clear at the top of the Premier League but Wenger, who has won the FA Cup four times, denies victory tomorrow will register a psychological blow in the title race.
"I feel United are still in contention. Two games ago we were second and that shows you how quickly it can change from one day to the next," he said.
"But it's always better to win because it makes you stronger. You want to win the big games because it makes your whole squad stronger."