Nigel de Jong has vowed to carry on crunching to keep the Blues on course for the top four.

The Dutch pitbull has been told to rein in his ferocious commitment by his national team coach Bert van Marwijk after an uncompromising challenge which broke the leg of Bolton's US midfielder Stuart Holden.

De Jong has already made it plain that he did not intend to hurt Holden, but has come under a barrage of criticism from across the Atlantic.

And now he has been warned by van Marwijk to adapt his style when he plays in the World Cup this summer - or risk being red-carded by zealous international referees.

"Nigel plays in England and that is the league where referees allow players to do so much more," said van Marwijk.

"A foul like the one Nigel committed on Holden can cost us the World Cup.

"As soon as the game was over, I got hold of him and I told him straight. Maybe he thought this foul was not even as bad as the ones in previous games but he really must get this out of is system."

De Jong has taken the advice on board, but insists there will be no holding back when the ball is there to be won at Sunderland on Sunday - or for the rest of the season.

"It's difficult because I always give 100 per cent," said de Jong. "I spoke with the coach but he knows how I am as a player.

"But I also have to know that with international referees you can't do certain things, as you can in England. Over here, they will play on for things that get stopped in international games.

"I just have to focus on my game and be smart in certain situations on the pitch."

De Jong has vowed to play smarter, not softer, especially when he pulls on the orange shirt of Holland. But the combative former Ajax and Hamburg star believes he has found his spiritual football home in the cut and thrust of the Premier League.

And he revealed that he grew up admiring the uncompromising midfield battles he watched, open-eyed, as a boy in Amsterdam.

"English competition suits me better than German or Dutch at the moment, so I am happy to be here and willing to give 100 per cent again this weekend," he said.

"For me there is no holding back - not until I go back to Holland for a game.

"If you hold back you are going to get injured or get a red card. When it's a 50-50 you have to go for it 100 per cent."

De Jong clearly regrets Holden's injury, which will keep him out of Bolton's fight for survival for six weeks.

"I had no evil intent," he said. "If the ball is between me and the opponent, you have to go in full. If you do not then the opponent takes you."

De Jong fears that over- emphasis on the dangers of full-blooded challenges are detrimental to the game, as tackling is an art and injury an occupational hazard.

"Because of the speed of the game and with everything that has gone on lately, tackling gets looked at more closely," he said.

"But it is a part of the game and a big part of English football culture.

"Usually it goes well, but sometimes it goes wrong, but like most players I never have the intention of breaking somebody's leg or of injuring anyone.

"I have always admired the physical side of the English game. I am not the type of player who can make a nice action and score a hat-trick.

"I am the type that goes into the midfield battle and tries to win the ball with a tackle.

"I used to love watching English football as a boy, to see the midfield generals, like Paul Ince, Roy Keane and Patrick Vieira when he was younger."

De Jong is an interesting character - as much as he is a fierce competitor on the field, and has the look of a Bond villain's henchman, he is an intelligent, affable type off it.

And as well as being midfield enforcer, he is the club's enterprise ambassador, encouraging kids from across Greater Manchester to take part in the Enterprise City scheme.

The Dragon's Den-style scheme aims to use City and the Eastlands stadium to teach children about business.

De Jong took a keen interest as the kids came up with possible new products to sell in the City shop, and had to come up with a plan to develop and market those products.

It is a subject close to de Jong's heart. Outside football, he is a successful businessman in his own right, owning a company which specialises in customising luxury cars for wealthy clients.

Based in Hamburg, the company now has branches in Holland and Abu Dhabi, and he was delighted to sit down and help the kids work through their own business schemes.

"I'm fortunate that I can have a business like that, because cars have always been my hobby.

"Now I'm lucky to have made a business out of it as well," he said.

"When you see how the kids put their business plans on paper, it gives you great joy. I have two kids, and it's good to see them thinking about this kind of thing at this age.

"Everyone wants to do things for themselves and make a little money and it's not easy in the current financial climate, but I've been telling the kids to just go for it."