Devin Toner is expected to be a shock omission from Ireland's 31-man World Cup squad.
The 33-year-old Leinster lock has numbered among Joe Schmidt's most trusted lieutenants, starting 50 of the Kiwi head coach's 67 Test matches as Ireland boss.
The PA news agency understands Munster's South Africa-born Jean Kleyn has been given the nod ahead of Toner in the squad Ireland submitted to World Rugby on Monday.
Ireland submitted their squad for the fast-approaching Japan tournament on Monday, but were not due to announce that roster until Sunday.
Meticulous planner Schmidt has wanted to wait until after Saturday's final warm-up fixture against Wales in Dublin before publicising Ireland's World Cup squad.
Schmidt and his coaches spent Sunday and Monday morning deliberating their selections however, and have since told governing body World Rugby of their 31-man line-up.
Kleyn only qualified for Ireland on residency two days before his Test debut, the 29-10 victory over Italy on August 10.
But now the 26-year-old appears to have edged out Toner, who has proved a lineout and restart banker throughout Schmidt's six years at Ireland's helm.
Leinster's Luke McGrath is thought to have been given the nod at scrum-half, at the expense of Connacht's Kieran Marmion, with Will Addison edging out Munster powerhouse Chris Farrell in a four-strong centre line-up.
Former England Under-20s star Addison adds crucial versatility to Ireland's ranks, able to operate at centre, wing, full-back and at a push fly-half.
Joey Carbery is understood to have been selected alongside Johnny Sexton and Jack Carty at fly-half.
Munster star Carbery is expected to be fit from his ankle problem in time for Ireland's opening World Cup Pool A clash, against Scotland on September 22.
Carbery will be Ireland's emergency scrum-half cover, with Schmidt opting to take just two recognised number nines.
