Fabien Bacella is the latest big-name Biarritz player to be doubtful for Saturday's clash with Gloucester at Kingsholm.
The French international prop, who has established himself as one of the game's most-feared front row forwards, is struggling with a knee problem.
Barcella suffered the setback during the 25-15 defeat at Stade Francias at the weekend and is now a possible absentee for the Round 5 encounter in England's West Country.
The news comes on the back of a double disappointment for the 2006 finalists after two of their most-experienced players were almost certainly ruled out of the Gloucester match.
Former France scrum-half Dimitri Yachvili, Biarritz's leading points scorer in Heineken Cup history and the club's first-choice goal kicker, and veteran centre Damien Traille will not make the trip to Gloucester.
Like Barcella, the duo picked up knocks in Saturday's loss in Paris.
They will be assessed further on Tuesday, with Biarritz hopeful they will return for the Round 6 encounter with Glasgow Warriors.
Biarritz currently head the group by 10 points from second-placed Gloucester, meaning a losing bonus point from either of their two remaining pool games will guarantee qualification for the knockout stages.
Finals Edition: Listen to the best guide to the European Rugby Cup Finals weekend in Dublin, which sees Leinster Rugby take on Stade Francais Paris at the RDS on Friday night in the Amlin Challenge Cup Final and then ASM Clermont Auvergne tackle Toulon in an all-French affair at the Aviva Stadium on Saturday.