Springboks Odwa Ndungane and Willem Alberts both failed to recover in time for the Sharks' Super Rugby encounter against the Stormers in Cape Town on Saturday.
Winger Ndungane picked up a shoulder injury in the build-up to last week’s defeat to the Bulls, while loose forward Alberts (also shoulder) had been sidelined for most of the pre-season.
Sharks coach John Plumtree, who also received bad news on Wednesday that Ryan Kankowski will be out for a month with a finger problem, said earlier this week that he was hopeful the other two Boks would be fit.
The coach has made four changes for the match at Newlands with Jacques Botes replacing Kankowski.
Captain Keegan Daniel shifts from blindside flank to number eight to accommodate Botes.
Also among the forwards, prop Jannie du Plessis drops to the bench with Wiehahn Herbst drafted into the starting XV, while Ross Skeate comes in at lock for Anton Bresler.
“Upfront, we want to give Wiehahn Herbst an opportunity,” Plumtree said.
“He's had a really good pre-season and it's a good time for him.
“We've had to make a change amongst the loose-forwards obviously with Ryan Kankowski out and with Jacques Botes playing really well against the Bulls last week, he gets a chance.”
In the back line, Tim Whitehead failed to overcome a groin complaint and misses out against his former club as Meyer Bosman takes his place at centre.
Lubabalo Mtembu and Marius Joubert are the two new faces on the bench.
Plumtree added: “It's disappointing for us that Willem Alberts hasn't made it this week, but Tera (Lubabalo) Mtembu has done pretty well in the pre-season, so it's an opportunity for him as well.”
Sharks team: Riaan Viljoen, Louis Ludik, JP Pietersen, Meyer Bosman, Lwazi Mvovo, Patrick Lambie, Frederic Michalak, Keegan Daniel (captain), Marcell Coetzee, Jacques Botes, Ross Skeate, Steven Sykes, Wiehahn Herbst, Bismarck du Plessis, Dale Chadwick.
Replacements: Craig Burden, Jannie du Plessis, Anton Bresler, Lubabalo Mtembu, Charl McLeod, Marius Joubert, Paul Jordaan. – Sapa