He said: "I have not dodged a challenge anywhere in my career. I have a lot to offer this club, although I know I haven't played to my full level as often as I would have liked. But my best is coming.
"It does not matter what you have achieved in the past, it is irrelevant. You always have something to prove.
"I have a four-year contract here and I will be running as hard in the last year of my contract as I did in the first year.
"I have seen people elsewhere who have played hard at the time of contract renewals and done enough to get what they wanted. Once they have the security of a long-term deal they ease off and don't perform the way they have previously.
"That happens sometimes but not at this club because the manager would not tolerate it."