Ireland captain Caelan Doris will miss July’s Nations Championship matches with Australia, Japan and New Zealand with a foot injury.
Back row Doris was forced off in the early stages of Leinster’s United Rugby Championship final win over the Bulls at Croke Park on Friday.
Leinster wing Tommy O’Brien has also been ruled out of the three summer matches with a groin injury.
Ulster duo Bryn and Zac Ward have been called up in place of the injured duo, while hooker Dan Sheehan will captain Ireland in the absence of Doris.
Andy Farrell’s side fly to Sydney on Monday ahead of the Nations Championship opener with Australia on 4 July.
Ireland then take on Japan on 11 July and New Zealand at Eden Park the following week in the other summer fixtures.
Losing both Doris and O’Brien is a blow for Farrell, who is also without fly-half Jack Crowley and key prop Andrew Porter.
Doris limped off in the seventh minute of the game but returned to lift the URC trophy and join in the celebrations with his team-mates at full-time.
Speaking after the game, he said he would get the injury “checked out” but it is severe enough to rule him out of all three summer matches.
O’Brien, who scored the opening try in Leinster’s Investec Champions Cup final defeat by Bordeaux, has had another impressive campaign but was also forced off against the Bulls with a groin issue.
The Ward brothers have been rewarded for an impressive campaign with Ulster, who now have 10 players in the Ireland squad after a much-improved campaign.
Wing Zac, 27, previously played for Ireland in Rugby Sevens and has featured in four Emerging Ireland and Ireland ‘A’ fixtures.
Back row Bryn, 21, had a breakthrough season with Ulster and played a key role as Richie Murphy’s side reached the Challenge Cup final, and he was also a training panellist for the Six Nations.