Coach Oleg Blokhin has admitted Andriy Shevchenko is not certain to play in Ukraine's World Cup opener against Spain on Wednesday.

The Chelsea striker has been struggling with a knee injury for the past six weeks, but made a goalscoring return to action as a second-half substitute in last Thursday's 3-0 friendly victory against Luxembourg.

However, the 29-year-old's display has not entirely convinced Blokhin that he is ready for the greater test posed by Spain.

"I can't say anything about Shevchenko's injury or whether he will play," Blokhin said.

"We'll just have to see over the next few days. It's not that I want to hide anything from the Spanish, it's just that I don't know.

"If he is not ready then we will play without him. With Shevchenko, Ukraine is one team and without him it is a completely different one."

Shevchenko, who has scored 29 times in 64 internationals, is more optimistic about his chances.

"I feel fine, just a bit tired. The knee feels good, as good as it can, but doctors have to decide," he said.

"I think I will be fit for Spain. I have talked a lot to Blokhin. He is trying to slow me down, saying not to hurt myself, that the team needs me."