Switzerland captain Alexander Frei faces surgery for the knee ligament tear which prematurely ended his involvement in EURO 2008, team doctor Cuno Wetzel said on Thursday.

The Borussia Dortmund striker suffered the injury in the opening Group A match last Saturday, a 1-0 defeat by the Czech Republic.

"He probably faces surgery," said Wetzel of Switzerland's star player, who has scored 35 goals in 60 internationals to be the leading scorer in Switzerland's history.

"He is doing OK (but) we have detected a certain instability" regarding the knee," Wetzel said. "We have spoken to his club doctors and undertaken further tests with a knee specialist in Germany. There are several possibilities. It will probably be necessary to carry out a little surgery."

Frei's loss has been compounded by form and fitness problems with his regular strike partner, Marco Streller, who Wetzel said also potentially faced surgery for a suspected hernia.

The Swiss bowed out of the EUROs after they went down 2-1 to Turkey on Wednesday in Basel.