Taulupe Faletau is expected to miss Wales' autumn internationals after breaking his arm in Bath's loss to Exeter last Friday.
No timescale has yet been put on the No 8's recovery but it is a major blow for Bath and Wales as he could realistically face a lengthy spell on the sidelines.
Bath kick off their Champions Cup campaign against Toulouse on Saturday, while Wales' autumn series opener against Scotland is on November 3, followed by Tests against Australia, Tonga and South Africa.
Faletau, 27, went off late in the game during Bath's 39-24 home defeat to the Chiefs.
Bath also face Wasps in the Champions Cup this month before they resume Premiership action by tackling Worcester on November 17.
Wales head coach Warren Gatland, meanwhile, is set to name his autumn Test squad next week.
And while back row is one of Wales' strongest areas, the potential loss of a player with 72 caps and who started all three Tests for the British and Irish Lions against New Zealand last year, would be a significant setback.