Marcell Coetzee did not travel with Sharks for their tour of New Zealand after the flanker sustained a knee injury in Saturday's Super Rugby derby defeat to Lions in Durban.
The South Africa international, who will join Ulster at the end of the Super Rugby season, was taken off on a stretcher during Sharks' 24-9 loss at Kings Park and it remains to be seen how long he will be out of action.
Sharks revealed on Sunday that Jean Deysel had replaced Coetzee in their squad for the trip to New Zealand, with more details on the Springbok's injury to be released "in due course".
Gary Gold, the Sharks coach, told Sport24 on Saturday: "It's not looking good. He's gone to hospital, he's had a scan... it's not looking great,
"We just hope that it's as minor as possible but there does seem to be a little bit of laxness in the knee which does suggest that at very best he won't be ready for next week."
Sharks, now without a win in three matches, face Blues next Saturday before taking on Highlanders and Chiefs.