James Anderson's participation in next month's first Investec Test against Pakistan appears in doubt because of a shoulder injury in his bowling arm.
The England and Wales Cricket Board has confirmed Anderson will definitely miss his scheduled return to action in Lancashire's Specsavers County Championship match against Nottinghamshire at Trent Bridge.
That match begins on July 3, with the four-Test series against Pakistan then getting under way at Lord's only 11 days later.
The ECB has yet to issue an official assessment of Anderson's injury, which has been reported elsewhere as a stress fracture of his right shoulder blade.
As England's all-time leading Test wicket-taker, and the world's number one bowler too for the first time after his outstanding success in this summer's series victory over Sri Lanka, Anderson's absence would be a major blow.
If he were not fit in time, England would need to make at least two enforced changes to the team which completed the series against Sri Lanka at Lord's this month - after it emerged two days ago that out-of-form batsman Nick Compton is to take a break from professional cricket.
Pace-bowling all-rounder Ben Stokes, who had to miss the final two Tests against Sri Lanka after pulling up in the first and then having knee surgery, was back on the field for the first time - as a 12th man and then specialist batsman only - with Durham this week.
His club and country team-mate Mark Wood, who has not played since last October's Dubai Test against Pakistan and has since had two ankle operations, is also due back for Durham this weekend.
Fast bowler Wood was part of England's Ashes-winning attack last summer, but he too will return initially as a specialist batsman only in a tour match which starts on Sunday against Sri Lanka A.