The Dutchman goes by a nickname of ‘Khalid the Cannibal’ but insists he always sets out to play by the rules.

Boulahrouz, 24, said: “My philosophy of football is quite easy. I go on the pitch and play only to win.

“I’m a defender so I have to do my job and that is to control the striker so he doesn’t score goals. I try to play fair. I don’t usually put somebody in the hospital or elbow somebody in the head.

“I don’t like that because I don’t need to do that. I try to control my player with fair play. I try to win. It gives me a kick when I control the striker fairly. I don’t like to use things like elbows or to tackle in a dangerous way.

“Sometimes people get injured, sometimes they don’t. This is football.”

Boulahrouz completed his £7m (€10.3m) transfer on Monday and goes straight into the squad for today’s game at Middlesbrough.

He told his new team-mates to call him ‘Boula’ rather than ‘Cannibal’ and claimed the nickname came about after a minor misunderstanding.

Boulahrouz said: “I went to Hamburg and my German was not so good. So I tried to explain with my hands and show some moves how I am on the pitch.

“The next day I opened the paper and it said ‘The Cannibal signs contract until 2008’. I didn’t say I eat attackers.”

Chelsea boss Jose Mourinho is fond of players who have fought their way up from humble beginnings.

Boulahrouz left the Ajax youth set-up and made his name under Martin Jol at RKC Waalwijk. He moved to Hamburg two years ago and was selected for Marco van Basten’s Holland squad for the World Cup.

Mourinho said: “Khalid is the kind of person I admire. Life was not easy for him and to be here as a 24-year-old he had to go through the process from a small club and then to Germany and the national team.

“Now he is at one of the best clubs in the world at the moment. He did that because of hard work and ambition and confidence and quality.”

Boulahrouz was sent off against Portugal at the World Cup and accused of deliberately trying to injure Cristiano Ronaldo.

He had a poor disciplinary record in the Bundesliga, but said: “In the German league they are not used to physical contact.

“Since I was young I’ve watched the Premier League and I like the way they play football. I came here to work hard and to experience playing at a big club.

“I always try to improve myself. I came here to make everybody happy. That’s not to play unfairly. I will play fairly and confidently and show people what my qualities are.”

Boulahrouz left Hamburg under a cloud, with suggestions he had faked an injury to secure his move to Chelsea.

The defender was due to play in a Champions League qualifier against Osasuna two weeks ago, but twisted his ankle in the warm-up and pulled out.

Hamburg suspected he had been told not to play by Chelsea, but Boulahrouz said: “Nobody is in a position to say such things. I had pain and could not play. That is the end of it.”