England hooker Luke Cowan-Dickie may be out for the rest of the season after rupturing knee ligaments.
Last week, the 28-year-old Exeter skipper limped off in the first half of England's Six Nations victory against Wales.
"It's a fairly serious injury. It's a surgical injury to a knee ligament with some cartilage damage "Exeter director of rugby Rob Baxter stated.
"He's going to be out for an extended amount of time, probably the remainder of the season."
It means that Saracens' Jamie George will be England's first-choice hooker for the rest of the Six Nations, with Newcastle's Jamie Blamire filling in.
Cowan-Dickie missed the start of the Premiership season after earning three Test caps for the British and Irish Lions last summer in South Africa.
The Cornishman then suffered ankle ligament damage in October, limiting him to just eight appearances for Exeter this season.
"It's a tremendous setback because he's a very important guy here and a very excellent player," Baxter told BBC Sport.
"We have some hope that he will play at the conclusion of the season, especially if we can extend the season by finishing in the top four, but it's too early to tell.
"He was there and cemented in as a starter in the England team, a member of their leadership group, and England was doing extremely well
