Key striker Jan Koller's thigh injury has been suspected a serious one, said Czech coach Karel Brueckner after his side started their World Cup debut in style with a 3-0 win over the United States in the Group E opener in Gelsenkirchen on Monday.

"Unfortunately his injury is very serious," said Brueckner. "It is the only shadow over today's otherwise perfect match."

But good news later arrived that Koller didn't tear anything.

"When I felt the pain, I thought now everything's over for me, but I'm glad that the scan said that nothing is torn," said the towering striker of Borussia Dortmund.

"After three to four days rest I will be able to train again. But I'm not sure if I make it for the next game," he added.

The 33-year-old, who scored the Czechs' first goal in 5 minutes, rolled over in the 42nd minute with a challenge from Oguchi Onyewuand was carried off on a stretcher while the challenge was not ruled as a foul.

"It's probably a thigh muscle and is a quite serious injury, although I cannot say exactly how serious." said Brueckner.

"Jan was extremely glad to be back in the starting eleven. He gave a good performance before this injury. This is really bad luck."

Tomas Rosicky, who scored double goals to drive the Czechs to the victory felt bad about Koller's injury.

"We may have lost Koller and that makes this game tough to take," he said.

The Czech has missed the only other established forward Miland Baros for the opening match due to a foot injury suffered in a warm-up match two weeks ago, and seen Pavel Nedved doubtful for next matches against Ghana and Italy after being hurt during Monday's game.

"The price of the injury of Koller is too high for our victory. We also lost Vladimir Smicer and Milan Baros before this game," said Rosicky. "We have to deal with these issues."

Koller, 2.02 meters tall, who has capped 69 times and scored 44 goals for the Czech team, has just returned from a serious knee injury sustained in September.