Roy Keane has warned Irish and Scottish footballers they must clean up their lives if they are ever to match their counterparts from other countries.
The former Republic of Ireland skipper believes many Barclays Premier League footballers, and particularly those not in their teams, could be fitter, and is appalled that is the case.
Keane, who also played in Scotland with Celtic, is adamant that both his compatriots and players from north of the English border are putting themselves at a disadvantage because of their off-the-field habits.
His comments came after Northern Ireland manager Nigel Worthington expressed his concern at the fitness levels of members of his squad who are struggling to get regular football with their clubs, something which is a concern for Republic of Ireland coach Giovanni Trapattoni.
The Sunderland boss said: "The English lads don't seem to be too bad - obviously, the French and the Spanish are good.
"But the players with the biggest problem in terms of changing their mentality are certainly the Irish and the Scottish players, because that's the way they have been brought up.
"That's the way I was brought up. I was brought up eating rubbish, drinking rubbish, so it is trying to change that mentality.
"You have to try to remind the players and provide these dieticians and speak to the players and eventually, you hope the penny will drop.
"You hope - sometimes it doesn't.
"I will go back to the game a few weeks ago, the United and Arsenal game.
"You have got to be able to sprint to people, you have got to play for 90 minutes.
"You can't be tiring after 45, 50 minutes, not in the Premier League. You can't do it."
Keane's squad is packed with Irish players - Paul McShane and Anthony Stokes, currently out on loan, as well as Liam Miller and Daryl Murphy, were away with the Republic this week, while Andy Reid has been a regular, and £9million Scotland keeper Craig Gordon is also on the books at the Stadium of Light, although currently injured.
The Black Cats have worked hard on educating their current crop, but the manager knows they can only do so much.
He said: "You can provide everything for them in terms of fitness coaches, the right foods, the right hotels or whatever it might be.
"But of course, you cannot follow players, you cannot follow players when they leave your training ground.
"I think a lot of players in the Premier League can be fitter. A lot of players have the excuse that they are not playing - yeah, but you can still get fitter, you can still do extra, still do swimming, still do more weights, get your body-fat down.
"I did it both ways. I was able to get away with it when I was younger, having high body-fat and not leading the right lifestyle.
"But the last six, seven, eight years of my career, you certainly wanted to be as fit as you possibly could.
"When you consider that's your career and that's your job...and particularly for players who are out of the team, get yourself fitter and you might get in the team.
"It's up to yourself. Nobody should really throw that at you if you are a professional sportsperson, that you are not fit enough.
"My God, that must hurt players."
Keane will hope all his players are in good shape as they prepare for Sunday's home clash with West Ham, and in particular, Trinidad and Tobago trio Kenwyne Jones, Dwight Yorke and Carlos Edwards in the wake of Wednesday night's 3-0 World Cup win over Cuba.
FIFA vice-president Jack Warner, a special adviser to the T&T Football Federation, has once again had his say this week over an alleged lack of respect shown by English clubs over their international players.
Keane, however, was in no mood to enter into dialogue with a man he has previously branded "a clown" and "a disgrace".
He said: "Maybe he should start looking at insurance for these players rather than getting worried about English clubs and stuff like that."
