| MD | Players | Club | Nationality | DOB | A(D) |
|---|---|---|---|---|---|
| 04-Dec-2020 |  Tommaso Menoncello | Benetton Treviso | Italy | 20-Aug-2002 | 18(107) |
| 02-Nov-2020 | Joe Hawkins | Ospreys | Wales | 11-Jun-2002 | 18(145) |
| 26-Feb-2021 |  Mason Grady | Cardiff Blues | Wales | 29-Mar-2002 | 18(335) |
| 28-Feb-2021 |  Jamie Osborne | Leinster | Ireland | 16-Nov-2001 | 19(104) |
| 24-Oct-2020 | Jamie Dobie | Glasgow Warriors | Scotland | 07-Jun-2001 | 19(139) |
| 27-Mar-2021 | Riccardo Favretto | Benetton Treviso | Italy | 18-Oct-2001 | 19(160) |
| 06-Mar-2021 | Gregor Brown | Glasgow Warriors | Scotland | 01-Jul-2001 | 19(248) |
| 12-Mar-2021 | Garyn Phillips | Ospreys | Wales | 14-May-2001 | 19(302) |
| 05-Dec-2020 | Ben Carter | Gwent Dragons | Wales | 23-Jan-2001 | 19(316) |
| 02-Oct-2020 | Federico Mori | Zebre | Italy | 13-Oct-2000 | 19(354) |
| 30-Jan-2021 |  Sam Costelow | Scarlets | Wales | 10-Jan-2001 | 20(20) |
| 12-Mar-2021 | Alex Soroka | Leinster | Ireland | 19-Feb-2001 | 20(21) |
| 29-Nov-2020 | Gwilym Bradley | Cardiff Blues | Wales | 10-Sep-2000 | 20(80) |
| 08-Nov-2020 | Jac Price | Scarlets | Wales | 04-Aug-2000 | 20(96) |
| 16-Nov-2020 |  Ethan McIlroy | Ulster | Ireland | 10-Aug-2000 | 20(98) |
| 02-Jan-2021 | Gianmarco Lucchesi | Benetton Treviso | Italy | 10-Sep-2000 | 20(114) |
| 02-Oct-2020 | Paolo Garbisi | Benetton Treviso | Italy | 03-Jun-2000 | 20(121) |
| 19-Feb-2021 | Aneurin Owen | Gwent Dragons | Wales | 19-Oct-2000 | 20(123) |
| 02-Nov-2020 | Josh Thomas | Ospreys | Wales | 30-Jun-2000 | 20(125) |
| 02-Jan-2021 | Andrew Smith | Leinster | Ireland | 21-Jul-2000 | 20(165) |
| 23-Oct-2020 | Filippo Alongi | Benetton Treviso | Italy | 27-Apr-2000 | 20(179) |
| 02-Jan-2021 | David McCann | Ulster | Ireland | 13-Jun-2000 | 20(203) |
| 16-Nov-2020 | Manuel Zuliani | Benetton Treviso | Italy | 26-Apr-2000 | 20(204) |
| 28-Feb-2021 | Oli Smith | Glasgow Warriors | Scotland | 07-Aug-2000 | 20(205) |
| 09-Nov-2020 |  Nathan Chamberlain | Edinburgh Rugby | Scotland | 14-Mar-2000 | 20(240) |
| 25-Oct-2020 | Jack Blain | Edinburgh Rugby | Scotland | 21-Feb-2000 | 20(247) |
| 23-Oct-2020 | Jac Morgan | Scarlets | Wales | 21-Jan-2000 | 20(276) |
| 08-Nov-2020 | Michael Milne | Leinster | Ireland | 05-Feb-2000 | 20(277) |
| 30-Nov-2020 |  Thomas Ahern | Munster | Ireland | 22-Feb-2000 | 20(282) |
| 02-Jan-2021 | Max O'Reilly | Leinster | Ireland | 26-Feb-2000 | 20(311) |
| 16-Jan-2021 | Rufus McLean | Glasgow Warriors | Scotland | 02-Mar-2000 | 20(320) |
| 19-Mar-2021 | Cian Hurley | Munster | Ireland | 25-Apr-2000 | 20(328) |
| 22-Mar-2021 | Charlie Savala | Edinburgh Rugby | Australia | 21-Apr-2000 | 20(335) |
| 09-Oct-2020 | Taine Basham | Gwent Dragons | Wales | 02-Nov-1999 | 20(342) |
| 15-Nov-2020 | Tiaan Thomas-Wheeler | Ospreys | Wales | 19-Nov-1999 | 20(362) |
| 19-Feb-2021 | Tom Clarkson | Leinster | Ireland | 22-Feb-2000 | 20(363) |
| 13-Mar-2021 | Cian Prendergast | Connacht | Ireland | 23-Feb-2000 | 21(19) |
| 23-Oct-2020 | Scott Penny | Leinster | Ireland | 22-Sep-1999 | 21(32) |
| 30-Nov-2020 | Alessandro Fusco | Zebre | Italy | 28-Oct-1999 | 21(34) |
| 19-Mar-2021 | Cormac Izuchukwu | Ulster | Ireland | 28-Jan-2000 | 21(51) |
| 02-Oct-2020 | Stewart Moore | Ulster | Ireland | 08-Aug-1999 | 21(56) |
| 14-Nov-2020 | Colm Reilly | Connacht | Ireland | 08-Sep-1999 | 21(68) |
| 10-Oct-2020 | Ryan Baird | Leinster | Ireland | 26-Jul-1999 | 21(77) |
| 13-Mar-2021 | Rio Dyer | Gwent Dragons | Wales | 21-Dec-1999 | 21(83) |
| 28-Mar-2021 | Marshall Sykes | Edinburgh Rugby | Scotland | 29-Dec-1999 | 21(90) |
| 23-Oct-2020 | Liam Turner | Leinster | Ireland | 22-Jul-1999 | 21(94) |
| 12-Mar-2021 | Dewi Cross | Ospreys | Wales | 06-Dec-1999 | 21(97) |
| 01-Nov-2020 | Josh Wycherley | Munster | Ireland | 22-Jul-1999 | 21(103) |
| 10-Oct-2020 | Ben Healy | Munster | Scotland | 29-Jun-1999 | 21(104) |
| 05-Feb-2021 | Niall Murray | Connacht | Ireland | 13-Oct-1999 | 21(116) |
MD = Match date,
DOB = Date of birth,
A(D) = Age(days).