In his much-publicised autobiography, former United manager Ferguson suggested Rooney’s qualities could be "swallowed up by a lack of fitness".
Yet Rooney, who has recently received praise for his physical condition, insists he has statistical evidence to prove there has been no change.
Rooney said of his fitness: "It was the same last season. I've got all the stats, so I know.
"The stats are pinned up around the training ground every day and after every game you always get your stats - and it's the same with England.
"It's something you can monitor in terms of how much work you are doing and sometimes you do need a bit of a rest, so that's what we do.
"I'm just saying it's the same as last season but it's been noticed this season."
Current United boss David Moyes acknowledges Rooney may need a break in the future, after playing 161 minutes of England's recent friendlies against Chile and Germany.
"With the intensity of his football and how well he is playing, I was hoping we could have got him some time off," said Moyes.
"Obviously, Roy (Hodgson) has to pick his teams and the games were important for him and I respect that but somewhere along the line I will need to give Wayne a breather.
"If I get an opportunity I might be able to give him a little bit of time off as he is incredible with his effort and work.
“We've seen a Wayne Rooney we all like and all enjoy watching but we can't run him into the ground all the time."
