Sam Prendergast has been given a huge boost by Ireland head coach Andy Farrell in being given the starting berth at fly-half for Saturday's Test with Australia at Lansdowne Road.
The 21-year-old is preferred to Jack Crowley, who started all of Ireland's matches as they retained the Six Nations title this year, after impressing in his first start against Fiji last Saturday.
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Prendergast, who was a star of the Ireland Under-20 side that won a Grand Slam and then reached the Under-20 world final in 2023, will partner Jamison Gibson-Park at halfback.
Such is Prendergast's precocity that two iconic Irish fly-halves Ronan O'Gara and Johnny Sexton made their debuts at 22 and 24 respectively.
"I think he deserves it," Farrell said of Prendergast at his post team announcement press conference.
"I thought he played pretty well.
"He has trained pretty well over the course of this autumn series as well, so there's another chance there to lead the week and grow in that manner."
Crowley started both the opening November defeat by New Zealand and the win over Argentina.
However, apart from the first half against the Pumas he looked far off the assured playmaker he had been at the Six Nations and then in the tied series with world champions South Africa in July.
Prendergast came on for Crowley in the second-half of the Argentina match and steadied the Irish, who just held on for a 22-19 win.
Farrell said Crowley, 24, had played well for Ireland but was still a work in progress.
"Jack's played very well for us for a good while now, played in a lot of big games as well," said Farrell.
"So we know as far as that's concerned what we've got, although there's a lot of improving to be had and to be seen with Jack."
Crowley will be on the replacements bench along with, amongst others, Cian Healy.
The 37-year-old prop will set a new Irish caps record of 134 should he come on on Saturday, edging one ahead of his former Leinster teammate Brian O'Driscoll.
Another Leinster stalwart, Garry Ringrose, has to be content with a place on the bench as Farrell has retained the centre partnership of Robbie Henshaw and Bundee Aki.
The latter rebounded in style against Fiji, having been dropped for the Pumas match, and was named man of the match.
Prendergast's fellow former Under-20 star Gus McCarthy is also retained after an eye-catching debut by the hooker last weekend.
He is on the replacements bench with Ronan Kelleher starting at hooker.
The Irish meet an Australia side coached by their former handler Joe Schmidt, who began their run of success, securing them the Six Nations Grand Slam in 2018.
Farrell has built on that and will hope to get the better of his former boss in a match that has special meaning to the hosts as it is to celebrate the 150th anniversary of Irish Rugby.
"Saturday's Test match is a significant milestone in the story of Irish rugby," said Farrell.
"Aside from the 150th celebrations, for Cian (Healy) it presents the opportunity to break the Test cap record, which is a remarkable achievement considering the robustness of his position.
"Cian is a giant of Irish rugby and we are determined to provide him with a performance that he deserves."
Ireland (15-1): Hugo Keenan; Mack Hansen, Robbie Henshaw, Bundee Aki, James Lowe; Sam Prendergast, Jamison Gibson-Park; Caelan Doris (capt), Josh van der Flier, Tadhg Beirne; James Ryan, Joe McCarthy; Finlay Bealham, Ronan Kelleher, Andrew Porter
Replacements: Gus McCarthy, Cian Healy, Tom O'Toole, Iain Henderson, Peter O'Mahony, Craig Casey, Jack Crowley, Garry Ringrose
