| 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 - Mülheim | 2021/09/25 10:30 | Christos Keisidis v Lawrence Bataljin | 6-4,5-3 |
| UTR Pro Tennis Series - Mülheim | 2021/09/24 08:00 | Christos Keisidis v Jurriaan Bol | 1-6,4-6 |
| UTR Pro Tennis Series - Mülheim | 2021/09/23 11:00 | Christos Keisidis v Artem Podorozhnyi | 5-7,2-5 |
| UTR Pro Tennis Series - Mülheim | 2021/09/22 14:00 | Colin Sinclair v Christos Keisidis | 6-3,6-1 |
| UTR Pro Tennis Series - Mülheim | 2021/09/21 08:00 | Edison Ambarzumjan v Christos Keisidis | 6-2,4-6,5-1 |
| UTR Pro Tennis Series - Sófia | 2021/09/03 07:00 | George Lazarov v Christos Keisidis | 6-4,6-4 |
| UTR Pro Tennis Series - Zadar | 2021/09/28 12:30 | Duje Kekez v Stefanos Sakellaridis | 7-6,6-3 |
| UTR Pro Tennis Series - Zadar | 2021/09/27 11:30 | Stefanos Sakellaridis v Drazen Petrovic | 7-6,2-6,5-2 |
| ITF - M25 Pardubice | 2021/09/22 11:05 | Daniel Siniakov v Stefanos Sakellaridis | 6-3,6-2 |
| ITF - M25 Pardubice | 2021/09/21 08:00 | Daniel Paty v Stefanos Sakellaridis | 3-6,3-6 |
| ITF - M25 Pardubice | 2021/09/20 09:00 | Christopher Patzanovsky v Stefanos Sakellaridis | 6-4,1-6,7-10 |
| UTR Pro Tennis Series - Říčany | 2021/09/19 07:00 | Lawrence Bataljin v Stefanos Sakellaridis | 0-6,6-6 |
| UTR Pro Tennis Series - Říčany | 2021/09/18 10:30 | Stefanos Sakellaridis v Michalis Sakellaridis | 6-2,7-6 |
| UTR Pro Tennis Series - Říčany | 2021/09/17 12:00 | Stefanos Sakellaridis v Petr Hajek | 6-7,2-6 |