Northampton Saints prop Brian Mujati suffered a calf injury in Sunday's 17-16 Aviva Premiership defeat to Saracens.
The former Springbok front-rower was forced off the pitch in the 36th minute.
And Saints director of rugby Jim Mallinder is not sure how long Mujati - set to leave Northampton for French club Racing Metro next season - will be sidelined for.
"Not too sure," said Mallinder.
"He injured his calf so I'm not exactly sure what the extent of the damage is. Hopefully it's not too bad."