The Spaniard was in imperious form for the Old Traford side during the match.
He made 14 saves to deny Arsenal a comeback.
“I told him after the match that what I saw today was the best goalkeeper in the world,” the Portuguese said. “In big matches you need goalkeepers to be there for you.”
The victory ended Arsenal’s 13-game unbeaten run at the Emirates with United now five points behind League leaders, Manchester City, who play on Sunday.