Ireland captain Caelan Doris has been forced out of their opening Nations Championship matches next month after suffering an injury in Leinster's United Rugby Championship triumph.Leinster hooker Dan Sheehan takes over as captain for the tests against Australia, Japan and New Zealand, the Irish Rugby Union said.Doris hurt his foot early in Leinster's runaway 36-7 victory over the Bulls at Crowe Park.Teammate Tommy O'Brien, who scored the opening try in Saturday's win (NZT), is also out of the trip with a groin issue.Ulster's uncapped brothers Bryn and Zac Ward have been named as replacements.The 21-year-old Bryn is a former Ireland Under-20 international who had only made nine appearances for Ulster before a call-up this year to Ireland's Six Nations squad.The 27-year-old Zac scored 15 tries in 20 games for Ulster this season. They are the sons of New Zealand-born former Irish international flanker Andy Ward.Ireland's plans had already been hit by injuries to flyhalf Jack Crowley and loosehead prop Andrew Porter, in addition to Ryan Baird, Shayne Bolton, Jack Boyle, Edwin Edogbo, Tom Farrell, Mack Hansen, Paddy McCarthy and Calvin Nash.The squad departs early this week to Sydney ahead of their opening game of the new competition against the Wallabies on 4 July.- Reuters