Cardiff - Wales loosehead prop Aaron Jarvis damaged a pectoral muscle in their win over the Springboks 11 days ago and is expected to be sidelined for about six weeks.
Jarvis was hurt as a replacement in the 12-6 win at Millennium Stadium.
His Ospreys regional team revealed the injury on Wednesday.
"He doesn't require surgery, but he is still looking at a recovery period of around six weeks," Ospreys medical performance manager Chris Towers said.
The Ospreys have already been dealing without props Nicky Smith (pectoral muscle), Ryan Bevington (groin) and Duncan Jones (ligaments).