| 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 - Nis | 2021/10/09 11:00 | Christos Keisidis v Lawrence Bataljin | 6-4,6-2 |
| UTR Pro Tennis Series - Nis | 2021/10/08 15:45 | Dusan Trunic v Christos Keisidis | 2-6,2-5 |
| UTR Pro Tennis Series - Nis | 2021/10/07 08:30 | George Botezan v Christos Keisidis | 6-3,6-3 |
| 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 11:30 | Christos Keisidis v Alexander Lazov | 6-3,0-6,3-6 |
| 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 - Nis | 2021/10/09 13:15 | Aleksandar Ljubojevic v Vladimir Popov | 4-6,5-7 |
| UTR Pro Tennis Series - Nis | 2021/10/08 18:15 | Petar Pjevcevic v Vladimir Popov | 2-6,6-0,5-1 |
| UTR Pro Tennis Series - Nis | 2021/10/07 14:00 | Duje Kekez v Vladimir Popov | 6-0,5-1 |
| UTR Pro Tennis Series - Nis | 2021/10/05 10:30 | Ivan Denisov v Vladimir Popov | 6-2,5-4 |
| UTR Pro Tennis Series - Nis | 2021/10/04 08:30 | Vladimir Popov v Lazar Radenkovic | 6-1,5-2 |
| 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 11:00 | Mick Lescure v Vladimir Popov | 1-6,4-6 |
| UTR Pro Tennis Series - Sofia | 2021/08/31 11:00 | Mihael Mihaylov v Vladimir Popov | 1-6,3-5 |