Japanese rider Ryuichi Kiyonari is battling to be fit for the MCE British Superbike Championship season finale at Brands Hatch.
Kiyonari has been ruled out of this weekend's penultimate round at Silverstone after injuring his shoulder in a motocross accident.
His place in the Samsung Honda team has been taken over this weekend by Freddie Foray.
Kiyonari visited Silverstone on Friday morning for further medical assessment of his shoulder but was declared unfit to race after undergoing X-rays and physio sessions.
“I am disappointed that I cannot race this weekend because I like Silverstone,” said Kiyonari.
“I had the crash on the motocross bike when I landed and initially I thought I might have broken my collarbone as it has been very painful.
“I have to thank the medical team here because they have helped me today and I feel happy that it is not worse because I really want to be back for Brands Hatch.”
Team manager Havier Beltran added: “I am obviously disappointed that Kiyo cannot race this weekend, but the time with the BSB medical team this morning and the assessment they have done here has been encouraging.
“Kiyo was originally concerned that it could have also aggravated an older injury, however it looks like that with some further treatment he should be able to race at Brands Hatch which is reassuring for him and will help his recovery.”
Kiyonari is currently in fifth position in the Showdown standings.