| UTR Pro Tennis Series Portoroz | 2021/08/29 08:00 | Olexiy Kolisnyk v Deni Zmak | 4-6,6-2,6-3 |
| UTR Pro Tennis Series Portoroz | 2021/08/28 07:00 | Egor Novikov v Deni Zmak | 2-6,7-6,1-5 |
| UTR Pro Tennis Series Portoroz | 2021/08/26 08:30 | Denis Parshutin v Deni Zmak | 3-6,0-6 |
| UTR Pro Tennis Series Portoroz | 2021/08/25 13:00 | Tilen Zitnik v Deni Zmak | 3-6,1-6 |
| UTR Pro Tennis Series Portoroz | 2021/08/24 07:00 | Deni Zmak v Timur Maulenov | 7-6,5-1 |
| UTR Pro Tennis Series Portoroz | 2021/08/22 10:00 | Deni Zmak v Oleksandr Bielinskyi | 6-2,7-6 |
| UTR Pro Tennis Series Portoroz | 2021/08/21 09:30 | Olexiy Kolisnyk v Deni Zmak | 4-6,6-7 |
| UTR Pro Tennis Series Portoroz | 2021/08/20 08:00 | Denis Parshutin v Deni Zmak | 3-6,1-5 |
| UTR Pro Tennis Series Sofia | 2021/09/03 07:00 | George Lazarov v Christos Keisidis | 6-4,6-4 |
| UTR Pro Tennis Series Sofia | 2021/09/02 07:00 | Vladimir Popov v Christos Keisidis | 7-6,6-7,3-6 |
| UTR Pro Tennis Series Sofia | 2021/09/01 08:00 | Christos Keisidis v Mario Radev | 6-1,4-6,6-4 |
| UTR Pro Tennis Series Sofia | 2021/08/31 08:00 | Christos Keisidis v Josh Sheehy | 4-6,4-6 |
| UTR Pro Tennis Series Sofia | 2021/08/30 07:00 | Christos Keisidis v Denislav Prodanov | 6-1,5-1 |
| ITF M15 Heraklion | 2021/06/09 08:00 | Antonio Cayetano March v Christos Keisidis | 4-6,7-6,6-2 |
| ITF M15 Heraklion | 2021/06/08 06:30 | Sean Hodkin v Christos Keisidis | 6-4,5-7,4-10 |
| ITF M15 Heraklion | 2021/06/07 09:00 | Christos Keisidis v Alexander Gaponenko | 6-4,6-1 |