Joe Calzaghe believes that Amir Khan has "learnt a hard lesson" following his defeat to Lamont Peterson in Washington on Saturday.
The 25-year-old lost the super lightweight fight by split decision which caused the former WBA and IBF light-welterweight champion to hit out at the referees' scores.
"He's still inexperienced, he's a young fighter and he will improve on this," Calzaghe told talkSPORT. "Unfortunately he had a rude awakening and if people think Amir Khan is the finished article, he is not but he will come on from this performance.
"He's still very young. He's done great to win the world titles at the age that he has. I boxed my best fights when I was 34 or 35-years-old.
"He's learnt a hard lesson from this fight and if he's looking at fighting the guys above this guy then he really needs to step up a level otherwise he will get beaten again."
The Bolton-born boxer has won 18 bouts by way of knockout in his career.