Ireland international hooker Richardt Strauss has been diagnosed with a heart condition and he will not play again this season.
Strauss, 27, is set to undergo surgery this week, his provincial team Leinster announced.
The South Africa-born player made his Ireland debut against the Springboks last year. He has won four caps, but missed the whole of last season's RBS 6 Nations Championship because of an ankle ligament injury.
"Following the result of extensive medical tests, it has emerged that Ireland hooker Richardt Strauss has been diagnosed with a heart condition and will be unavailable for selection for the remainder of the season," Leinster said, in a statement.
"The management are confident that the 27-year-old, who is set to undergo surgery this week, will make a full recovery and will provide him with the best care in his recovery."
Strauss joined Leinster in 2009 and he has been an integral part of their squad since then, playing key roles in the 2010 and 2012 Heineken Cup final victories over Northampton and Ulster, respectively.
Leinster, meanwhile, rate star centre Brian O'Driscoll as having a 50-50 chance of being fit for next Saturday's Heineken opener against the Ospreys in Swansea.
O'Driscoll is nursing a calf muscle strain, and Leinster say at this stage he has not been ruled out of the selection mix.
South Africa international back Zane Kirchner could also be in the frame for next weekend after linking up with his new team-mates following commitments in the Rugby Championship.