Fast bowler Simon Jones will miss Glamorgan's Yorkshire Bank 40 clash against Leicestershire on Wednesday because of a shoulder injury.
The rest of the squad in Southend on 9 June continue at Grace Road.
Glamorgan lie fourth, a place behind the Foxes, in Group C on seven points having won three games this season.
The hosts have won four of their six matches as they and Glamorgan chase for knock-out places.
However, group leaders Somerset underlined their credentials with a five-wicket win over Leicestershire on Sunday.
MA Wallace (wicketkeeper), WD Bragg, CB Cooke, MJ North (capt), MW Goodwin, J Allenby, BJ Wright, GG Wagg, DA Cosker, WT Owen, AJ Jones and MG Hogan.