| UTR Pro Tennis Series Portoroz | 2021/08/18 12:30 | Yanais Laurent v Colin Sinclair | 5-7,5-7 |
| UTR Pro Tennis Series Portoroz | 2021/08/17 11:00 | Jan Vehovec v Colin Sinclair | 2-6,1-5 |
| ITF M15 Sofia | 2021/07/06 09:50 | Colin Sinclair v Dragos Nicolae Madaras | 3-6,2-6 |
| ITF M25 Belgrade | 2021/06/30 07:00 | Colin Sinclair v Edoardo Eremin | 2-6,1-6 |
| UTR Pro Tennis Series Bucharest | 2021/05/23 07:00 | Nicolae Frunza v Colin Sinclair | 5-6 |
| UTR Pro Tennis Series Bucharest | 2021/05/22 12:30 | Ilya Snitari v Colin Sinclair | 6-4,6-7,6-7 |
| UTR Pro Tennis Series Bucharest | 2021/05/22 07:00 | Colin Sinclair v Simon Beaupain | 6-3,6-4 |
| UTR Pro Tennis Series Bucharest | 2021/05/19 10:00 | Colin Sinclair v Juan Ignacio Galarza | 4-6,2-6 |
| UTR Pro Tennis Series Portoroz | 2021/08/17 11:00 | Yanais Laurent v Aleksa Pisaric | 6-4,5-1 |
| UTR Pro Tennis Series Portoroz | 2021/08/16 11:00 | Aleksa Pisaric v Tilen Zitnik | 6-3,4-6,6-1 |
| ITF M15 Novi Sad | 2021/08/02 12:30 | Aleksa Pisaric v Dusan Obradovic | 2-6,2-6 |
| ITF M25 Belgrade | 2021/06/27 07:00 | Viktor Jovic v Aleksa Pisaric | 7-6,6-3 |