| UTR Pro Tennis Series Portoroz | 2021/08/29 08:00 | Kolisnyk, Olexiy v Zmak, Deni | 4-6,6-2,6-3 |
| UTR Pro Tennis Series Portoroz | 2021/08/27 12:00 | Kolisnyk, Olexiy v Gostincar, Domen | 7-6,6-3 |
| UTR Pro Tennis Series Portoroz | 2021/08/25 10:00 | Kolisnyk, Olexiy v Uzhylovsky, Vladimir | 6-1,6-1 |
| UTR Pro Tennis Series Portoroz | 2021/08/25 07:00 | Kolisnyk, Olexiy v Vladan Tadic | 6-2,3-6,2-1 |
| UTR Pro Tennis Series Portoroz | 2021/08/24 08:30 | Nik Razborsek v Kolisnyk, Olexiy | 5-7,6-2,2-6 |
| UTR Pro Tennis Series Portoroz | 2021/08/21 09:30 | Kolisnyk, Olexiy v Zmak, Deni | 4-6,6-7 |
| UTR Pro Tennis Series Portoroz | 2021/08/20 11:00 | Kolisnyk, Olexiy v Lawrence Bataljin | 6-3,6-2 |
| UTR Pro Tennis Series Portoroz | 2021/08/18 08:00 | Botezan, George v Kolisnyk, Olexiy | 5-7,1-6 |
| UTR Pro Tennis Series Nis | 2021/10/10 08:00 | Keisidis, Christos v Vladimir Popov | 6-1,5-2 |
| UTR Pro Tennis Series Nis | 2021/10/09 11:00 | Keisidis, Christos v Lawrence Bataljin | 6-4,6-2 |
| UTR Pro Tennis Series Nis | 2021/10/08 15:45 | Dusan Trunic v Keisidis, Christos | 2-6,2-5 |
| UTR Pro Tennis Series Nis | 2021/10/07 08:30 | Botezan, George v Keisidis, Christos | 6-3,6-3 |
| UTR Pro Tennis Series Nis | 2021/10/05 14:00 | Aleksa Mardjonovic v Keisidis, Christos | 2-6,7-5,6-4 |
| UTR Pro Tennis Series Nis | 2021/10/04 11:30 | Keisidis, Christos v Lazov, Alexander | 6-3,0-6,3-6 |
| UTR Pro Tennis Series Zadar | 2021/10/03 09:30 | Admir Kalender v Keisidis, Christos | 6-2,6-0 |
| UTR Pro Tennis Series Zadar | 2021/10/02 11:30 | Keisidis, Christos v Ivan Denisov | 3-6,6-1,6-5 |