Craig Casey has emerged as an injury doubt for Ireland's upcoming Six Nations campaign.
The scrum half picked up a shoulder problem in Munster's 27-25 defeat to Toulon in the Champions Cup yesterday.
Munster now need to beat Castres next week to book their place in the knockout stage.
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In the Challenge Cup, Connacht coughed up a 17-point lead to slump to a 33-31 defeat to Montpellier away from home.
Ulster were awarded a 28-nil win over the Toyota Cheetahs after their match in the Netherlands was cancelled due to an unplayable pitch.
