Glamorgan fast bowler Timm van der Gugten did not make a first-team return in the opening One-Day Cup match against Gloucestershire at Bristol on Thursday.
The 26-year-old damaged his shoulder playing for Netherlands in February and missed Glamorgan's first three Championship games.
He took three wickets for Glamorgan's second XI on his return on Tuesday.
But post-match soreness prevented Van der Gugten's first-team return.
Craig Meschede and Owen Morgan were added to the squad.
Nick Selman dropped out of the squad with David Lloyd set to open the batting.
Batsman Will Bragg has made a successful return after back trouble, scoring 93 in a second eleven fixture against Gloucestershire in Newport.
Glamorgan captain Jacques Rudolph hopes that playing eight Cup games in a row for the first time will benefit the side, who won their first three but lost the next four in 2016.
"It will just keep our focus for that specific format, I always speak about momentum and it's important we hit the ground running," Rudolph told BBC Wales Sport.
"The guys are excited about playing white-ball cricket again and it's generally a format we pride ourselves on."
Gloucestershire are a wily team and they play well in their own conditions, so we've got to know how we want to go about our business, and get some early momentum."
Gloucestershire welcome back one-day captain Michael Klinger to their squad among a series of changes from their Championship side.
Gloucestershire: M Klinger (c), P Mustard, C Dent, I Cockbain, G van Buuren, B Howell, J Taylor, K Noema-Barnett, T Smith, M Taylor, L Norwell, C Liddle, C Miles.
Glamorgan: J Rudolph (c), D Lloyd, C Ingram, C Cooke, A Donald, K Carlson, C Meschede, O Morgan, A Salter, M de Lange, T van der Gugten, M Hogan, L Carey.