Kevin Pietersen could miss England's first Test against the West Indies at Lord's after tearing a calf muscle.
Pietersen was England's leading runs scorer in the Ashes
Pietersen was forced out of Hampshire's Championship match with Lancashire after suffering the injury playing for his county against Ireland on Monday.
"It is extremely annoying," he said. "The muscle is torn and I'll have to see how it responds to treatment before I know if I'll be able to play."
The squad for the Test, starting on 17 May, will be revealed on Sunday.
Michael Vaughan will almost certainly miss the match after breaking the middle finger of his right hand while batting for Yorkshire on 3 May.
Pietersen, 26, was one of the few players to emerge from the disastrous trip to Australia last winter with his reputation intact.
In the Test series his top score was 158 and he hit three half-centuries before being ruled out of the one-day series with a cracked rib, although he regained fitness to play in the World Cup where he averaged 55.
"What I do know is that I'm desperate not to miss it and will do everything I can to get fit," he told in the Daily Mail.
The England and Wales Cricket Board said Pietersen had undergone an MRI scan and his injury would be assessed again "later in the week".
It looks like some inexperienced batsmen will be selected on Sunday, after Marcus Trescothick confirmed he was not ready to return to England colours despite hitting a double hundred for Somerset.
Middlesex duo Owais Shah and Ed Joyce will be among the names discussed as potential replacements.