Wales number eight Taulupe Faletau has broken his arm on the eve of the Six Nations.
The 28-year-old suffered the break playing for Bath against Wasps on Saturday, a game which marked his return from another broken arm sustained in October.
"Bath Rugby can confirm that Taulupe Faletau suffered a fracture to his forearm in Saturday's Heineken Champions Cup fixture against Wasps," his club said in a statement.
"It's not yet known at this time how long Taulupe will be out of action."
Faletau is expected to be out for up to eight weeks, with the final round of Six Nations fixtures coming on March 16.
Wales begin their campaign away to France on February 1 and coach Warren Gatland is due to announce his squad at 12pm on Tuesday.
Faletau's injury is just one of a number of injury problems facing Gatland, with Leigh Halfpenny, Dan Biggar and Adam Beard all suffering with injuries.
Gatland was due to make further checks on Rhodri Jones (shoulder), James Davies (knee), Nicky Smith (ankle), Dan Lydiate (elbow), Rhys Patchell (hamstring), Jake Ball (shoulder) and Bradley Davies (knee).