Lakeside Hammers are expecting to lose reserve rider Stuart Robson for a number of weeks.
The 34-year-old suffered rib and lung injuries while riding for doubling-up side Newcastle last week.
He missed last night's narrow 47-43 defeat at Wolverhampton, which earned Lakeside one Elite League point.
"He will need time to recover but, hopefully, we won't have seen the last of him this season," Hammers promoter Jon Cook told the team website.
"Although his injuries are serious he looks to have avoided the leg and wrist injuries first reported."
Meanwhile, Polish heat leader Piotr Swiderski will remain on the sidelines with an ankle injury, after a failed comeback in his homeland on Sunday.