| UTR Pro Tennis Series - Nis | 2021/10/07 10:00 | Aleksa Mardjonovic v Alexander Lazov | 2-6,4-5 |
| UTR Pro Tennis Series - Nis | 2021/10/06 11:30 | Aleksa Mardjonovic v George Botezan | 6-4,5-3 |
| UTR Pro Tennis Series - Nis | 2021/10/05 14:00 | Aleksa Mardjonovic v Christos Keisidis | 2-6,7-5,6-4 |
| UTR Pro Tennis Series - Nis | 2021/10/04 10:00 | Aleksa Mardjonovic v Dusan Trunic | 6-3,6-2 |
| ITF M15 Pirot | 2021/09/21 12:25 | Aleksa Mardjonovic v Kristijan Juhas | 2-6,4-6 |
| ITF M15 Pirot | 2021/09/20 11:00 | Paul Valsecchi v Aleksa Mardjonovic | 4-6,6-4,6-10 |
| ITF M15 Pirot | 2021/09/19 12:30 | Dusan Trunic v Aleksa Mardjonovic | 4-6,6-2,7-10 |
| ITF M15 Zlatibor | 2021/09/15 13:20 | Aleksa Mardjonovic v Petar Pjevcevic | 6-1,3-6,3-6 |
| UTR Pro Tennis Series - Nis | 2021/10/08 14:15 | Stefan Ivic v Veljko Krstic | 6-4,3-6,1-5 |
| UTR Pro Tennis Series - Nis | 2021/10/07 08:30 | Lawrence Bataljin v Veljko Krstic | 7-6,3-6,5-7 |
| UTR Pro Tennis Series - Nis | 2021/10/05 09:30 | Ivan Liutarevich v Veljko Krstic | 5-7,6-4,6-2 |
| UTR Pro Tennis Series - Nis | 2021/10/04 08:30 | Veljko Krstic v Oleksandr Bielinskyi | 5-7,6-1,6-3 |
| ITF M15 Zlatibor | 2021/09/16 09:40 | Oleksandr Ovcharenko v Veljko Krstic | 6-1,6-1 |
| ITF M15 Zlatibor | 2021/09/14 11:10 | Tomislav Jotovski v Veljko Krstic | 4-6,1-6 |
| ITF M25 Bělehrad | 2021/06/29 10:40 | Skander Mansouri v Veljko Krstic | 7-6,7-5 |