Boxing: Frank Warren believes Nathan Cleverly must impress against Robin Krasniqi

Nathan Cleverly (left) finds the ribs of Tommy Karpency in Cardiff (Getty Images)

Promoter Frank Warren believes WBO light-heavyweight champion Nathan Cleverly must impress in his title defence against Robin Krasniqi if he is to fight Bernard Hopkins.

Cleverly, 26, faces Krasniqi at Wembley Arena on 20 April, with a bout against Hopkins, who won the IBF belt at the weekend, the target. "Nathan can't afford to slip up because if he does, any potential fight against Bernard Hopkins will go out of the window," said Warren.