Connacht prop Nathan White will miss Ireland's autumn Test series after rupturing a tendon in his upper arm in training with Joe Schmidt's squad.
The New Zealand-born tighthead faces surgery next week and could now be sidelined for as long as four months.
The 33-year-old was lined up for his international debut against South Arica next weekend. His absence further drains Ireland's already stretched front-row resources.
The former Leinster front-rower had been expected to understudy Mike Ross across the autumn series, with Marty Moore already out for three months after shoulder surgery.
Now head coach Schmidt and Ireland will be pinning hopes on Leinster's experienced front-rower Ross recovering from groin trouble as expected to shore up Ireland's scrum.
Leinster's 34-year-old scrum cornerstone Ross is expected to return to full training next week. With White the latest star to lengthen Ireland's injury glut, his return gains even greater importance.
The big-scrummaging Springboks would have looked to take on Ireland's set-piece even if the Aviva Stadium hosts were at full strength up front next weekend.
White's absence, allied to Moore's shoulder surgery, leaves Ireland short of experience at tighthead for the South Africa clash.
Schmidt had admitted he promoted White into the squad for his potential debut on the strength of his lengthy top-level club career, expecting the 33-year-old to handle Test intensity better than several promising but young and raw prospects.
Now the former Leinster coach must draw on Connacht's versatile front-rower Rodney Ah You and Munster's Stephen Archer as potential understudies to Ross.
Former schoolteacher Schmidt should at least be able to call on Jack McGrath at loosehead prop as he aims to step up his return from injury, offsetting somewhat Cian Healy's long-term absence.
Ireland will still be shorn of at least 15 stars for the visit of Heyneke Meyer's Springboks, however, before entertaining Georgia and then Australia across the three-Test Guinness series.