The recurrence of an elbow injury has ruled Saracens prop Cobus Visagie out of action until November.
Visagie had initially suffered the problem while training as part of South Africa's squad earlier in the summer.
But the problem returned, and Visagie has been forced to undergo surgery.
Saracens rugby director Alan Gaffney said: "It is a blow, both for Cobus and for Saracens, but he needed to have the surgery and as a result is expected to miss the first two months of the season.
"With Cencus Johnston away with Samoa and Matias Aguero and Kevin Yates in with a chance of making selection for the World Cup, it could leave us a bit short of props in the early part of the season, so that is something we will have to look at resolving."
However, Saracens have been looking to bolster their squad elsewhere and have captured the signature of Springbok number eight Guthrie Hall.
Hall was part of the Natal Sharks' squad in both the Super 14 and Currie Cup competitions last season.