Stadium: Court 5 Round: 25 Ground: Hardcourt indoor
| ITF M15 East Lansing | 2021/11/16 15:00 | Mercer, J v Mostardi, Nico | 1-6,5-7 |
| ITF M15 East Lansing | 2021/11/15 18:00 | Miralles, Borja v Mostardi, Nico | 6-3,2-6,4-10 |
| ITF M15 Ithaca | 2021/11/05 14:00 | Johnson, Luke v Mostardi, Nico | 6-0,6-0 |
| ITF M15 Ithaca | 2021/11/04 14:00 | Mostardi, Nico v Guy Orly Iradukunda | 6-3,3-6,6-4 |
| ITF M15 Ithaca | 2021/11/03 14:00 | Mostardi, Nico v Credit Chaiyarin | 6-4,6-2 |
| ITF M15 Ithaca | 2021/11/02 14:30 | Mostardi, Nico v Leblanc, Alexandre | 7-6,4-6,7-10 |
| ITF M15 Ithaca | 2021/10/06 16:35 | Mostardi, Nico v Charles Broom | 1-6,6-7 |
| UTR Pro Tennis Series Dallas | 2021/08/08 15:30 | Evan Zhu v Mostardi, Nico | 6-4,5-0 |
| ITF M15 Ithaca | 2021/11/04 16:45 | Colin Sinclair v Kirkov, Vasil | 3-6,4-6 |
| ITF M15 Ithaca | 2021/11/03 17:55 | Michael Zheng v Colin Sinclair | 0-6,2-6 |
| ITF M15 Tallahassee | 2021/10/27 14:00 | Colin Sinclair v Shane, Ryan | 6-3,3-6,6-7 |
| ITF M15 Ithaca | 2021/10/05 16:00 | Taha Baadi v Colin Sinclair | 7-6,7-5 |
| ITF M25 Budapest | 2021/09/28 10:45 | Pawel Juszczak v Colin Sinclair | 6-2,7-6 |
| UTR Pro Tennis Series Mulheim | 2021/09/25 13:30 | Colin Sinclair v Guy Den Heijer | 2-6,3-5 |
| UTR Pro Tennis Series Mulheim | 2021/09/25 10:00 | Colin Sinclair v Weng, Jing Long | 6-1,6-4 |
| UTR Pro Tennis Series Mulheim | 2021/09/23 11:00 | Colin Sinclair v Jurriaan Bol | 6-3,6-3 |