Iain Henderson is out of Ireland's summer tour of South Africa after undergoing toe surgery.
The Ulster skipper will miss the URC end of season run in for the province, including Saturday's vital Kingspan Stadium clash with Leinster, after going under the knife on Monday.
Ulster have confirmed that Henderson will need three months rehab to recover.
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The news comes as a blow to new Ulster head coach Richie Murphy and to Ireland boss Andy Farrell, who will want as strong a squad as possible to be available for the two-Test tour against the reigning world champions.
However Henderson, who was a starter in the World Cup quarter-final against New Zealand last October, found himself down the second row pecking order in the Six Nations, with Joe McCarthy making a splash as a starter.
Farrell will be at least pleased that Leinster lock James Ryan has recovered from bicep surgery and is available to the province again.
Ulster, meanwhile, are without centre James Hume, who also had surgery on Monday, and Luke Marshall (concussion) and Rob Baloucoune (hamstring) are also ruled out, joining Marty Moore, Jake Flannery, Ben Moxham and Callum Reid on the casualty list.
The province also have doubts over Tom O'Toole and Sean Reffell for Saturday as they come into the clash on the back of three URC victories on the spin.
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