Skipper Rory Best has been ruled out of Ireland's three-Test tour in Australia because of a hamstring injury.
Munster hooker Niall Scannell has been chosen as the Ulster man's replacement for the trip which involves Tests in Brisbane, Melbourne and Sydney.
Head coach Joe Schmidt indicated that Johnny Sexton and Peter O'Mahony could share the Irish captaincy.
Schmidt also said Leinster's versatile back Joey Carbery, who is in the tour squad, had agreed to move to Munster.
The Test matches against Australia take place on 9, 16 and 23 June.
Best sustained the injury while training for Ulster and had to sit out the club's final-game 35-17 win over Ospreys which secured a place in next season's European Champions Cup.
"He had a hamstring issue that kept him out of the game against Ospreys and we felt he was really going in the right direction and he would be ready for game one [against Australia], definitely for game two. But he's just not quite where we need him to be," said Schmidt.
"Because a number of these things have just become apparent, we've two vice captains in Peter O'Mahony and Johnny Sexton and a strong leadership group.
"It will depend a bit on selection and what we feel we need at any given time. It could be that Pete and Johnny take the team on and share the load."
Scannell, who has won seven caps for Ireland, will join Leinster's Sean Cronin and Rob Herring of Ulster as the three hookers in the 32-man squad for the Test series in Australia.