The prop sustained his injury during the opening quarter of the match and was forced off the field, heading straight to A&E at Worcestershire Royal Hospital, before a follow-up appointment at Morriston Hospital Fracture Clinic, where the bad news was confirmed.
Ospreys Head Physio, Chris Towers, said:
"Cai has broken a bone in the left forearm and will be in plaster for a period of six to eight weeks. Given this, he is looking at being out of action for two to three months depending on how his recovery goes."
Guinness PRO12
Suite 208, Alexandra House,
The Sweepstakes
Ballsbridge, Dublin 4, Ireland