Worcestershire seamer Matt Mason lasted just six overs on his comeback from a rib injury.
Mason, who is also the county's bowling coach, has yet to make a first-team appearance this season.
He aggravated the rib problem in pre-season and broke down again almost immediately on his return to action for the second XI in a friendly against Derbyshire at RGS Worcester.
The Australian, who is now likely to seek further medical opinion, joins Alan Richardson, Chris Whelan and David Wheeldon in the treatment room at New Road.
Richardson has had an injection in his ankle and should be fit to open the bowling in the next County Championship fixture at home to Derbyshire, starting on May 17.
Fellow seamer Whelan is battling to overcome a hamstring injury in time to face Derbyshire but batsman Wheeldon is out until at least the start of June with a broken thumb.