| UTR Pro Tennis Series Zadar | 2021/10/03 09:30 | Admir Kalender v Christos Keisidis | 6-2,6-0 |
| UTR Pro Tennis Series Zadar | 2021/10/02 11:30 | Christos Keisidis v Ivan Denisov | 3-6,6-1,6-5 |
| UTR Pro Tennis Series Zadar | 2021/10/01 08:00 | Christos Keisidis v Drazen Petrovic | 6-4,6-4 |
| UTR Pro Tennis Series Zadar | 2021/09/30 09:30 | Christos Keisidis v Stefanos Sakellaridis | 4-6,6-4,6-4 |
| UTR Pro Tennis Series Zadar | 2021/09/29 08:00 | Duje Kekez v Christos Keisidis | 6-2,2-6,5-6 |
| UTR Pro Tennis Series Zadar | 2021/09/28 12:30 | Janos Fekete v Christos Keisidis | 6-4,5-3 |
| UTR Pro Tennis Series Mulheim | 2021/09/25 10:30 | Christos Keisidis v Lawrence Bataljin | 6-4,5-3 |
| UTR Pro Tennis Series Mulheim | 2021/09/24 08:00 | Christos Keisidis v Jurriaan Bol | 1-6,4-6 |
| UTR Pro Tennis Series Ricany | 2021/09/18 09:00 | Antonin Bolardt v Alexander Lazov | 4-6,6-4,2-5 |
| UTR Pro Tennis Series Ricany | 2021/09/16 07:00 | Alexander Lazov v Jan Satral | 1-6,2-6 |
| UTR Pro Tennis Series Ricany | 2021/09/15 12:00 | Alexander Lazov v Yanais Laurent | 4-6,6-1,3-5 |
| UTR Pro Tennis Series Ricany | 2021/09/14 09:00 | Alexander Lazov v Yann Wojcik | 6-4,3-6,6-7 |
| UTR Pro Tennis Series Ricany | 2021/09/13 12:00 | Alexander Lazov v Michael Gloeckler | 6-3,6-3 |
| UTR Pro Tennis Series Sofia | 2021/09/04 07:30 | Alexander Lazov v George Lazarov | 3-5 |
| UTR Pro Tennis Series Sofia | 2021/09/03 07:00 | Alexander Lazov v Dian Nedev | 7-5,5-3 |
| UTR Pro Tennis Series Sofia | 2021/09/01 09:30 | Yurii Dzhavakian v Alexander Lazov | 7-6,7-6 |