Tottenham's Defoe: Man Utd striker Rooney needs to play "on the edge"
The Manchester United star is known for his short fuse.
And Defoe said: "People say top players, or talented people, always seem to be a little crazy.
"But if you look at life in general, people who have got that gift are a little bit crazy and they live on the edge for some reason.
"It's important for Wayne to have that fire. I think you need that fire to achieve anything."