"His stats don't show that he doesn't work hard. The stats are good," Fergie told the club's official website.
"Like a lot of talented players, he's economic with his running. His movement and ability to find space is fantastic.
"He pops up where defenders don't want him to pop up. That's what I always thought when he played against us.
"I used to think 'Why has nobody picked him up?' He's got great awareness and finds good space in the box.
"His awareness and passing ability in the last third of the field is absolutely outstanding, but I still don't think we're using him enough, I really don't."