Glamorgan Wanderers have suffered a blow before the derby clash against Cardiff at the Arms Park in the Principality Premiership on Saturday.
Top points scorer Scott Sneddon pulled up in training on Tuesday and Mark Roper has stepped in to the outside half berth.
However, Blues centre Dafydd Hewitt is available as is Jason Pocock who came off early last week with an eye injury.
Captain Nick Kelly returns to the second row after appearing in the back row last week but prop Scott Andrews drops down to the bench due to his commitment with the Blues U-20's. Ben Warbuton, brother of Wales U-20's captain, Sam. joins the squad for the first time this season after putting some excellent performances for Merthyr on dual registration.
Nearly 40 players were involved in the first Wales Under 18 training session of the season. WRU National Performance Manager Gethin Watts is excited at the potential shown by the group and expects the Regional Under 18 Championship to hone their skills even further.