Chris Harris has broken his collarbone during Birmingham Brummies' Elite League meeting at Eastbourne Eagles.
The 31-year-old, who joined the Brummies from Coventry in December, crashed out into the fence in his final ride in Monday's race.
"He has been returning to top form recently so this couldn't have come at a worse time for us," team boss Phil Morris told the club website.
The length of his absence has not been confirmed by the club.
The Brummies are currently top of the Elite League table, level on points with Wolverhampton.