The 9-6 win at Parc y Scarlets sealed second place in the Championship table for Ireland with all the points that night coming from the boot of Andrew Burke who is on the replacements for this play-off game.
Danny Barnes, called up for the injured Nevin Spence, starts at centre alongside Eamonn Sheridan.
The Irish back-three has a familiar look to it with Ian Madigan at full back, flanked by David Kearney and Michael Keating.
Up front, team captain Peter O'Mahony is part of a strong back row unit which also includes the Exiles' Rhys Ruddock and UL Bohemians clubman Brian O'Hara.
In the front row, IrishRugby.ie blogger Tom Sexton cements a solid trio packing down with Jack McGrath and Adam Macklin.
Ireland will be aiming for a place in the 5th-6th place play-off final against either Samoa or France next Sunday.
IRELAND UNDER-20 TEAM & REPLACEMENTS (v Wales, IRB TOSHIBA Junior World Championship, Wednesday, June 17, Level 5 Stadium, Fukuoka, kick-off 5pm local time/9am Irish time):
15 - Ian Madigan (Blackrock College/Leinster)
14 - David Kearney (Lansdowne/Leinster)
13 - Danny Barnes (UCC/Munster)
12 - Eamonn Sheridan (Lansdowne/Leinster)
11 - Michael Keating (Clontarf/Leinster)
10 - Ian McKinley (UCD/Leinster)
9 - Conor Murray (Garryowen Munster)
1 - Jack McGrath (St. Mary's College/Leinster)
2 - Thomas Sexton (Old Belvedere/Leinster)
4 - Dominic Ryan (Lansdowne/Leinster)
5 - Mark Flanagan (UCD/Leinster)
6 - Rhys Ruddock (Millfield School/Exiles)
7 - Brian O'Hara (UL Bohemians/Munster)
8 - Peter O'Mahony (Cork Constitution/Munster) (capt)
16 - David McGregor (Ballynahinch/Ulster)
17 - Paddy McAllister (Ballynahinch/Ulster)
18 - Joe Moran (Galwegians/Connacht)
19 - David O'Callaghan (UCC/Munster)
20 - Matthew Healy (Lansdowne/Leinster)
21 - Andrew Burke (Garryowen/Munster)
22 - Jonny Shiels (Queen's University/Ulster)
Related Links -
Tom Sexton's Japan Blog - The latest news from inside the Irish Under-20 camp thanks to hooker Tom Sexton.
IRB TOSHIBA Junior World Championship - all the news from the tournament.