Plymouth Devils captain Ben Barker will miss the rest of the season after breaking his leg against Sheffield.
Barker will have an operation on the leg, which he previously broke in 2009, and will be replaced in Friday's match against Ipswich by Emiliano Sanchez.
"It is a blow to be without our number one, but I am sure the other riders will rise to the challenge," said promoter Mike Bowden.
Plymouth are six points adrift at the bottom of speedway's Premier League.
"I was encouraged by the way the rest of the team responded to beat Sheffield last week when Barker had to pull out of the meeting after the first race," added Bowden.