The Manchester United star is no longer the firebrand he was in his younger days, too often flying off the handle at any little problem.
But the 24-year-old, who aims to down Bayern Munich in the Champions League, retains an ultra-competitive edge that occasionally requires an outlet.
Goal hero: Prolific Rooney scores against CSKA Moscow
When those situations occur, Rooney is happy to pull the boxing gloves on, as he learned to do when he was still at school.
'I used to do boxing and football,' he told Champions magazine. 'I was training every night with one of them and when I got to about 15, Everton said I had to stop boxing if I wanted to carry on playing football. I had a good chance of making the first team, so I stopped.
Pride of Manchester: Rooney supports Ricky Hatton (centre), posing with Marco Antonio Barrera in Las Vegas in June 2007
'I still love watching boxing. It is a big thing in my family. I canstill do a bit now after training, but obviously not fighting. I enjoyit. It is a good way to get rid of some anger.
Sir Alex Ferguson hopes there will be no reason for Rooney toget angry in the Allianz Arena as the striker returns from a bruisedfoot for the quarter-final first-leg tie.
Anger management: Rooney clashes with Dermot Gallagher during his Everton days
Rooney has establishedhimself as one of the most feared forwards in Europe thanks to his33-goal contribution to United's season.
However, Ferguson believes it is the presence of another England man who missed Saturday's four-goal destruction of Bolton that is even more crucial to United's chances of recording a record seventh successive away win in the competition, £29.1million defender Rio Ferdinand.
Ready for action: Rooney trains with United in Munich
'The return of Ferdinand and Vidic to keep our back four solid is significant,' said Ferguson.
'Along with Edwin van der Sar there was a time when all those players were injured. It wasn't easy and we were very fragile.
'But you can see the solidity now. You can see the experience of these players and it is making a massive difference to the performances of the team.
'It is a true saying strong at the back, strong as a team. We are looking very strong now.'
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