Andy Hazell will miss six weeks of action for Gloucester after undergoing surgery on a broken thumb.
The 33-year-old suffered the injury during the club's defeat to Northampton despite playing in the following match against Worcester.
"Hazell's had surgery, he broke his thumb against Northampton but he thought it was alright," coach Bryan Redpath told BBC Gloucestershire.
"It's a huge loss for us because he drives everything we rely on. He's Mr Gloucester, because he's always been here."
The flanker needed pins to be inserted in his thumb after a medical assessment.