The Swede, even at the age of 35, has taken English football by storm, netting 17 goals since arriving on a free in July.
Rooney, on the other hand, has struggled to maintain his influence under Jose Mourinho, managing just one Premier League goal all season.
Cascarino, initially critical of Ibrahimovic and Mourinho, insisted that the Englishman can learn a few things from Zlatan.
“His [Zlatan’s] fitness is extraordinary,” he said. “When you have a senior player like him, it makes the manager’s job easier,”
“Younger United players have spoken of how in awe they are of his attitude to training and the extra work he has been doing with his personal trainer. That means Jose Mourinho can point to Ibrahimovic when he is showing the other players what they should aspire to. He’s working harder than you even though he is 35 and has won everything.
“You hope that the penny might drop for Rooney, who should see the message.
“When you reach the last stage of your career, you have to be more professional than ever. I remember what it was like when you know you are nearing the end, and you start to fear it. In those years, I did nothing other than football – my whole life was devoted to it, eating properly, sleeping properly, doing everything right.”
There are some players that don’t seem as if they need extensive training in order to function at the highest level: Paul Gascoigne, Dimitar Berbatov, Edgar Davids, Eric Cantona are potent examples – the kind of players that could stay at home all week, turn up on match-day and steal the show.
Such was the case with both Ibrahimovic and Rooney during their earlier years. Neither player had what you would call a ‘conventional’ footballing physique; they espoused an air of rawness, of natural brilliance.
But time is a cruel mistress, and English football has the capacity to sap even the brightest of talents. Maintaining such levels of technical prowess, strength, speed and mental awareness in your thirties requires hard work, and nobody has mastered it better than Ibrahimovic. And Rooney, who looks to be heading in the opposite direction, could definitely take heed from the Swede’s indefatigable work ethic.