Exeter back Tommy Wyatt could be out until December after injuring his ankle.
It is the latest problem for the 26-year-old, who returned from a serious knee injury this summer, only to damage his shoulder in the final game of pre-season.
Wyatt came off in the first half of Exeter's European Champions Cup loss at Toulouse having played Exeter's previous three games.
It add more pressure to Exeter's strained backs division ahead of Saturday's Prem game at Bristol (17:30 BST).
Winger Campbell Ridl is out for the season, England's Immanuel Feyi-Waboso has a hamstring issue while Paul Brown-Bampoe and Olly Woodburn are also injured.
"The initial prognosis is it's not operable," Exeter director of rugby Rob Baxter told BBC Sport.
"So he should be back either late in the Prem Cup period or as we get back into the Premiership hopefully if things go well.
"It was another significant injury to a back three player which we seem to be we seem to be stacking up pretty quickly.
"You've got to feel for him, but it's part of the game now and you've kind of got to get on with it."