Fisher dislocated his right shoulder diving to prevent a boundary as Yorkshire slipped to a five-wicket defeat at Queen’s Park on Saturday.
It is yet another body blow to the highly-rated 21-year-old, who had only just recovered from a stress fracture of the back and a broken thumb.
Fisher cut a distraught figure in the immediate aftermath of the game, emerging with his arm in a sling and with Yorkshire unable to put a time-frame on his return.
“Until he’s seen a specialist we don’t know how long he’s going to be out for,” said first-team coach Andrew Gale.
“It’s his bowling shoulder, which is never good, and I’m really gutted for the lad because he’s worked so hard and put so many hours in the gym to get back on the park, but he just seems to have had one injury after another.
“He basically dislocated his shoulder diving and flicking the ball back, and although the shoulder popped back in as he came off the field, it’s not good,
“Fish has been brilliant for us the last few games, and I’m absolutely gutted for him because he’d just started to hit his straps again.”
Fisher’s injury capped a disappointing day for Yorkshire, who lost with five balls to spare after scoring 164-8 from their 20 overs.
It was Yorkshire’s fifth successive T20 defeat to Derbyshire and their fourth in succession at Queen’s Park, where they have not won a T20 fixture since 2014.
“The curse of Chesterfield continues,” said Gale.
“We haven’t won there for a few years now and, for whatever reason, we can’t seem to get over the line at this ground.
“To be honest, I thought the wicket was very, very poor for a T20 game.
“Why they put us on a used pitch, on a Championship wicket, I thought that was pretty average by Derbyshire to be fair.”
Yorkshire return to action tomorrow against Leicestershire at Grace Road.