Hamburg - Hoffenheim striker Vedad Ibisevic has undergone a successful operation on his injured right knee, the German league leaders said Saturday.

The Bundesliga's top scorer with 18 goals tore his cruciate ligament in a friendly game against SV Hamburg during a training camp in Spain on Wednesday.

The Bosnia striker had surgery at St Elisabeth hospital in Heidelberg and will be out for the rest of the season.

Swiss forward Eren Derdiyok has meanwhile turned down an approach. from Hoffenheim who are now in the market for a replacement striker.

The Basel striker has been reported as saying he would be joining fellow Bundesliga side Bayer Leverkusen at the end of the season.

Hoffenheim's billionaire investor Dietmar Hopp told Bild newspaper Saturday he backed a new signing but was "pessimistic of finding a replacement in such short time."

Hopp said he would give a chance to Brazilian striker Wellington, who was signed for 5 million euros (6.65 million dollars) last summer but has yet to establish himself in the side. (dpa)