Andriy Shevchenko, who scored both goals in the 2-1 victory over Sweden in their opening game, suffered two painful blows to his knee in Friday's match against France, Ukraine spokesman Oleksander Hlyvinsky said.
Co-hosts Ukraine lost 2-0 to France and have to beat England in Donetsk to go through to the last eight.
Hlyvinsky said the injuries sustained by the 35-year-old Shevchenko had generated fluid on the knee that doctors were trying to drain off.
Shevchenko's absence would be a huge blow to Ukraine who have struggled defensively and rely heavily on the attacking instincts of the former AC Milan and Chelsea player.
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