Wales have suffered a huge blow ahead of the Six Nations with Taulupe Faletau ruled out for between 12 to 16 weeks.
The timeframe will see him miss the start of the championship with the injury he suffered against Toulon on Saturday. He sustained a 'grade three medial knee ligament injury' which puts him out of action for at least three months.
"We're really disappointed for Taulupe -- he's been in great form this season, so it's really unfortunate news," Bath boss Todd Blackadder said. "However, he's in great hands with the medical team and we look forward to having him back on the pitch soon.
"These are opportunities where players can step up, and I've been thoroughly impressed by the way the likes of Paul Grant and Zach Mercer have performed over the last few weeks, and I'm sure they'll continue to do so."
The news will come as a huge disappointment to Bath and Wales. He is widely regarded as one of the world's top No.8s and impressed for the British & Irish Lions in their series draw with the All Blacks earlier this year.