Joey Carbery will start at outhalf against the US Eagles on Saturday as Paddy Jackson only links up with the Ireland squad when they move to Japan next week.

Jackson did not travel to New Jersey due to personal reasons, which also ruled him out of the historic victory over New Zealand in Chicago last November when Carbery won his first cap off the bench for the injured Johnny Sexton.

Munster centre Rory Scannell, and, at a stretch, Ulster-bound scrumhalf John Cooney, provide outhalf cover for the Test match at the Red Bull Arena (live on Eir Sport, kick-off 10pm).

Right about now Ireland could have done with a certain 27-year-old former Connacht player not slipping through their academy net. AJ MacGinty, Carbery’s fellow Blackrock College graduate, will wear number 10 for the US Eagles.

Carbery will also need to kick the goals despite his rare exposure to this crucial task with Leinster this season when the 21-year-old mainly played fullback. He has been mentored by Ronan O’Gara and Richie Murphy last week in Carton House and since arriving America on Monday.

Joey Carbery is set to start at outhalf on Saturday morning. Photograph: Tommy Dickson/Inpho

The other 21-year-olds – Andrew Porter, Jacob Stockdale and James Ryan – that helped Ireland reach the Junior World Cup final in 2016 are in line to win their first caps, probably off the bench.

That would signify a huge leap, especially by Porter, who only switched from loose to tighthead in recent months. The 125kg prop has recently been working with Mike Ross but he’s featured only once at tighthead for Leinster, against Ulster on May 6th, along with a handful of starts for UCD in the AIL.

The promotion of Stockdale, having impressed for Ulster this season, is no surprise, while the highly rated Ryan’s imminent arrival failed to materialise this season due to a hamstring injury.

“Individually you’d know they’re pretty switched-on guys,” said Ireland forwards coach Simon Easterby. “They’re pretty rugby-bright as well, so they’re a step ahead of maybe other players in their age group. Physically they’re obviously in a fairly good position as well.”

If capped, Ryan would be the first player to play for Ireland before Leinster since Michael Bent. It was Brian O’Driscoll before that.

“It is a win at all costs,” said Garry Ringrose. “It’s always the case when you put on the green jersey.”

Ringrose cemented his place in the Irish midfield this season but seven months ago he was an unused sub for the 40-29 defeat of the All Blacks.

“It is a bit of a roller-coaster,” he said. “I was involved in all of the Six Nations games which was a big learning experience for me. A lot of rugby has been played since November.”

And a lot of rugby may follow as it is widely accepted that Ringrose is on the injury reserve list for the Lions.

“It’s the least of my worries, I feel so lucky to go and represent Ireland for the next three weeks against USA and Japan. This time last year I missed out on a summer tour.”

He’s here now, for the time being anyway.

IRELAND (possible): S Zebo; T O’Halloran/J Stockdale, G Ringrose, L Marshall, K Earls; J Carbery, K Marmion; C Healy, N Scannell, John Ryan; Q Roux, D Toner; R Ruddock (cap), J Van der Flier/D Leavy, J Conan.

Replacements: D Heffernan, D Kilcoyne, A Porter, James Ryan, J van der Flier/D Leavy, L McGrath, R Scannell, J Stockdale/T O’Halloran.