Hallam Amos' inclusion in the senior trial means Afan Bagshaw will play in Wales Under-20's friendly against Scotland on Wednesday, 14 May.
Newport Gwent Dragons full-back Amos is in the "Probables" squad for the Wales trial match on 30 May in Swansea.
It means Rygbi Gogledd Cymru' Bagshaw is included as coach Byron Hayward prepares for the Junior World Cup.
"It's great to be able to have a really physical run out against Scotland," said Hayward.
The tournament takes place in New Zealand from 2 June to 20 June.
Despite Hallam Amos leaving the squad to contend for a spot on the Wales tour South Africa, Hayward has confidence in his group of players, who face the Scots at Bridgend's Brewery Field.
"Obviously it is a loss for us," said Hayward, a former Wales fly-half.
"However, Hallam has a great chance to be picked for South Africa and it won't affect our squad in so much as Hallam wasn't part of our Six Nations squad.
"Afon has been an integral part of the group all season and this gives him the chance to progress his game further."
Wales U20: Afon Bagshaw (RGC); Tyler Morgan (Dragons), Harri Evans (RGC), Steffan Hughes (capt, Scarlets), Dafydd Howells (Ospreys); Angus O'Brien (Dragons), Luc Jones (Dragons); Nicky Smith (Ospreys), Elliot Dee (Dragons), Nicky Thomas (Ospreys), Joe Davies (Dragons), Rory Thornton (Ospreys), Olly Cracknell (RGC), Scott Matthews (Dragons), James Benjamin (Dragons)
Replacements: Ethan Lewis (Blues), Luke Garrett (Dragons), Benjamin Leung (Scarlets), Scott Andrews (Dragons), Ben Roach (Blues), Connor Lloyd (Scarlets), Ethan Davies (Dragons), Jack Dixon (Dragons), Joshua Adams (Scarlets), Ashley Evans (Ospreys), Ollie Griffiths (Dragons), Scott Otten (Ospreys), Callum Lewis (Blues)
Scotland U20: Gavin Parker (Exeter Uni); Sam Pecqueur (Edinburgh Accies), Chris Dean (Edinburgh Accies/ Scotland Sevens), Neil Herron (Glasgow Hawks / Scotland Sevens), Damien Hoyland (Melrose); Rory Hutchison (Northampton Saints), Ben Vallacott (Worcester Warriors / Hartbury); Jack Cosgrove (Worcester Warriors), Sam James (London Wasps), D'arcy Rae (Ayr/ Galsgow Warriors), Andrew Cramond (Aberdeen Grammar), Glen Young (Newcastle Falcons), Neil Irvine-Hess (Watsonians/ Edinburgh Rugby), Tommy Spinks (capt, London Scottish), Gabriel Carroll (Loughborough Uni)
Replacements: Isaac Miller (Loughborough Uni), Phil Cringle (Edinburgh Accies/ Edinburgh Rugby), Zander Fagerson (Glasgow Hawks), Lewis Carmichael (Melrose), Shaun MacDonald (Stirling County), Ruaridh Knott (Loretto School / Melrose), Hugh Fraser (Merchiston School), Blair Hutchinson (Loughborough Uni/ Melrose), Ruairidh Young (Edinburgh Accies), Ben Chalmers (Melrose), Gavin Lowe (Glasgow Warriors/ Glasgow Hawks), Jamie Farndale (Edinburgh Accies / Edinburgh Rugby)