Law loves Rooney's on-field attitude.
He told the Daily Star Sunday: "There was a lot of controversy in the summer about whether he was staying or going but you feel that's all behind him now.
"Since he came to the club he has shown that he's not only a goalscorer but a person who tries, no matter what the scoreline is.
"That's what he was like even at 4-0 in the derby.
"That's what you need in your team. You're trailing but you have got to keep fighting. I had two great managers in my career - Bill Shankly early on at Huddersfield and, of course, Sir Matt Busby.
"They never gave up either. The message was always the same - the game is not over until the referee blows his whistle at 90 minutes.
"No matter what the score is, you keep trying.
"It's something that's certainly been instilled in United players ever since I was at the club. You don't give up."
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