Nick Timoney, Craig Casey and Sean Jansen will start for Ireland against Argentina in the Nations Championship on Friday night, with Jamison Gibson-Park and Josh van der Flier on the bench at Aviva Stadium.
With captain Caelan Doris and two-tour British and Irish Lion Jack Conan missing through injury, Connacht's Jansen always seemed the most likely to fill in at number eight for head coach Andy Farrell.
The 27-year-old made a try-scoring debut for Ireland against Japan in July and followed that with a cameo as a replacement against the All Blacks a week later.
The selections of Casey and Timoney, however, were less expected.
Influential scrum-half Gibson-Park has arguably been Ireland's best performer in recent seasons.
The 34-year-old missed the start of Leinster's season with a groin injury but made his return in the win over Munster on 24 October.
With only that game under his belt this season, he will start on the bench with Casey preferred to start at nine in a half-back partnership with fly-half Sam Prendergast, who has recovered from a wrist injury.
Ulster back row Timoney, 31, previously struggled to regularly break into the side despite strong form for his province, but selection against Argentina means he will be involved in his ninth consecutive Test.
Seven of those appearances, however, have been from the bench and his start on Friday night comes at the expense of former World Rugby player of the year Van der Flier.
With Garry Ringrose ruled out because of a hamstring problem, the experienced Robbie Henshaw will wear the 13 jersey, forming a midfield partnership with Stuart McCloskey.
Wing Mack Hansen, prop Andrew Porter and Ryan Baird all start, having not featured for Ireland since the defeat by South Africa in November 2025.
All three missed the Six Nations and summer fixtures in the Nations Championship through injury.
Hansen starts in the number 11 jersey in what is Ireland's first home game since James Lowe's departure from Irish rugby, with Robert Baloucoune keeping his spot on the right wing and Hugo Keenan selected at full-back.
Baird is selected at blind-side flanker, joining Timoney and Jansen in the back row.
Porter's return at loose-head will be a considerable boost for coach Farrell after recent windows were impact by injury problems at the position.
He will pack down alongside hooker Dan Sheehan, who captains the side in Doris' absence, and tight-head Tadhg Furlong.
Furlong is free to play after he was cleared by a disciplinary committee of grabbing Gavin Coombes in the groin last month.
Sam Illo, who will make his home debut if called upon, Ronan Kelleher, Tom O'Toole, Ciaran Frawley and Bundee Aki are Ireland's other replacements.
Argentina boss Felipe Contepomi has made 12 changes from the side that drew 28-28 with Australia in September as Los Pumas seek a first away win over Ireland.
Toulouse full-back Juan Cruz Mallia returns to win a first cap since November 2025 after injury.
Ireland: Hugo Keenan; Robert Baloucoune, Robbie Henshaw, Stuart McCloskey, Mack Hansen; Sam Prendergast, Craig Casey; Andrew Porter, Dan Sheehan (capt), Tadhg Furlong; Joe McCarthy, Tadhg Beirne; Ryan Baird, Nick Timoney, Sean Jansen.
Replacements: Ronan Kelleher, Tom O'Toole, Sam Illo, James Ryan, Josh van der Flier, Jamison Gibson-Park, Ciaran Frawley or Jamie Benson, Bundee Aki.
Argentina: Juan Cruz Mallia; Bautista Delguy, Justo Piccardo, Santiago Chocobares, Mateo Carreras; Tomas Albornoz, Gonzalo Garcia; Boris Wenger, Julian Montoya (capt), Francisco Moreno; Guido Petti, Pedro Rubiolo; Juan Martin Gonzalez, Marcos Kremer, Pablo Matera.
Replacements: Leonel Oviedo, Mayco Vivas, Joel Sclavi, Efrain Elias, Juan Martin Scelzo, Simon Benitez Cruz, Geronimo Prisciantelli, Lucio Cinti.