Wladimir Klitschko claimed that he needs to improve despite a unanimous points victory over Alexander Povetkin in Moscow on Saturday.
The 37-year-old retained his WBO, IBO, IBF and WBA titles by knocking Povetkin down four times en route to taking it with the decision, but the Ukrainian thought that he should have ended the fight sooner.
"I wanted to finish it earlier. I wanted to land that one big punch and I think I could have done better," Klitschko is quoted as saying in the Daily Mail.
"Alexander is a fighter and it was hard for him because I hurt him.
"[However] he stuck in there because he has a big heart."
The clash was the second richest fight in heavyweight history, behind only Mike Tyson's 2002 loss to Lennox Lewis.
