Canadian lock Jamie Cudmore has said that Clermont did not handle his concussion correctly, which could lead the second-rower to sue his former club.
During the European Cup, Cudmore was pulled off the field after colliding heads with Billy Vunipola. But minutes later he was called back onto the field after a team-mate was also injured.
The second-rower says that the damage to his brain could take a drastic effect on his life and that it was irresponsible of the French club.
"There was a huge head contact with Billy and myself going head to head at a ruck," Cudmore told the Daily Mail.
"It’s an accident of rugby, two guys arriving at the same time at the same height. We were both on our hands and knees. When I got back to the changing room they started to stitch me up and then after that they put me through the HIA.
"I had no chance. I probably remembered one of the words and I remember clear as day, I can see his face now, saying – No, you’re done."
The Clermont team doctor asked if Cudmore would get his boots back on and return to the game after very clearly being concussed.
"Jamie, Jamie, how are you? Sebby (Vahaamahina) is not good. Can you come back on? You got to come back on.
"I was like – Yeah, sweet – and tied my lace and went straight back out.
"Two or three minutes into the game I hit Chris Masoe and their other prop behind him at the same time and was just sparked straight out. It was a normal tackle leading with the shoulder. There was no contact with my head. But the force of the impact sparked me straight out. My body just went limp.
"I went off, did the HIA and a new doc we had figured everything was all right and I went back on. Towards the end of the game I had a clash of heads with Juan Smith and cut myself. I went off and started vomiting in the changing room. I didn’t know about second impact syndrome. I didn’t know I could have died.
"I definitely worry about the future. I don’t want to be one of those guys who is 65 but can’t remember anything."
Cudmore left Clermont after 11 years at the end of last season, signing for Oyonnax.