| 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 Bucharest | 2021/05/18 10:00 | Colin Sinclair v Tomas Lipovsek Puches | 6-2,5-1 |
| UTR Pro Tennis Series Bucharest | 2021/05/17 12:30 | Nicholas David Ionel v Colin Sinclair | 6-7,4-5 |
| ITF M15 Novomoskovsk | 2021/05/25 12:30 | Michal Dembek v Artem Podorozhnyi | 6-1,6-2 |