Gloucester flanker Andy Hazell has been ruled out for around six weeks after undergoing surgery on a broken thumb.
But further assessments revealed he would need pins put in his thumb.
"Hazell's had surgery, he broke his thumb against Northampton but he thought it was alright," coach Bryan Redpath told BBC Gloucestershire.
"He played against Worcester, and obviously it wasn't alright.
"It was flapping about so he's had pins put in it so he's out for six weeks - he had surgery on Monday morning.
"It's a huge loss for us because he drives everything we rely on. He's Mr Gloucester, because he's always been here.
"Credit it to him playing against Worcester - fair play to him."