So far this season, Rooney has one goal in seven appearances and the debate rambles on as to where his best position on the pitch is.
"Rooney is a special player. Strong, fantastic quality, shooting, vision - very intelligent," Nani told Omnisport.
"I enjoyed playing with him. He is a player who is a big part of Man United. He has chance to improve that and build his story.
'"If he continues to play at high level he can become the best there."