Speaking to the MU Podcast, Rooney said: "We knew we should've had it. I'll always remember to this day the biggest mistake the manager made was not putting me in goal.
"I used to practice in training after I'd finished all my stuff. I'd go with the goalie coach and the goalies and I'd go and practice kicking with the keepers, I'd practice saves. I was just energetic and had too much energy.
"I always remember saying if a keeper got sent off any time he'd have to put me in. I think he was probably worried I wouldn't have saved it and then we're 1-0 down and he'd need me to try and score.
"I think because he was the biggest. After that game I think Portsmouth went and played Middlesbrough and Cardiff or Millwall (sic), someone like that in the semi-final and final. I just remember looking at it thinking.
"I remember the boss, I think it was about two weeks he didn't speak to us."