Following his brace against Fulham on Sunday, Rooney has already scored 32 goals this season.
Berbatov scored United’s third in the game against Fulham.
“I think at the moment he’s the best,” said Berbatov. “And he is still so young so he has plenty of chances to get even greater. Like I’ve told him many times, just stay healthy and you can achieve everything.
“I think Wayne can certainly get over 40 goals. He still has plenty of games left so I wish him luck and we will all help him get over the 40 mark.”