Stadium: Court 2 Round: 14 Ground: Clay
| Challenger Warsaw | 2021/08/26 13:00 | Lucas Miedler v Szymon Kielan | 7-5,6-4 |
| Challenger Warsaw | 2021/08/25 08:00 | Szymon Kielan v Goncalo Oliveira | 7-5,6-0 |
| ITF M15 Lodz | 2021/08/19 10:30 | Daniel Michalski v Szymon Kielan | 3-6,7-5,6-3 |
| ITF M15 Lodz | 2021/08/18 09:30 | Roman Andres Burruchaga v Szymon Kielan | 6-7,3-6 |
| ITF M15 Gdynia | 2021/08/12 10:25 | Szymon Kielan v Alexis Musialek | 3-6,4-6 |
| ITF M15 Gdynia | 2021/08/11 14:25 | Luke Johnson v Szymon Kielan | 1-6,6-7 |
| ITF M25 Grodzisk Mazowiecki | 2021/08/04 17:10 | David Poljak v Szymon Kielan | 7-5,6-3 |
| Polish National Tour | 2021/07/11 10:00 | Kamil Majchrzak v Szymon Kielan | 6-1,7-6 |
| Challenger Kyiv | 2021/09/09 08:00 | Sebastian Baez v Alex Rybakov | 6-4,6-2 |
| Challenger Kyiv | 2021/09/07 07:00 | Alex Rybakov v Mohamed Aziz Dougaz | 5-7,6-0,6-3 |
| Challenger Kyiv | 2021/09/06 08:00 | Alex Rybakov v Aleksandr Braynin | 6-3,6-4 |
| Challenger Kyiv | 2021/09/05 08:00 | Alex Rybakov v Nikita Mashtakov | 6-2,6-2 |
| Challenger Prague | 2021/08/25 12:25 | Michael Geerts v Alex Rybakov | 6-2,6-2 |
| Challenger Prague | 2021/08/24 10:15 | Johannes Haerteis v Alex Rybakov | 4-6,2-6 |
| Challenger Prague | 2021/08/23 08:00 | Nick Hardt v Alex Rybakov | 6-7,3-6 |
| Challenger Prague | 2021/08/22 08:00 | Marek Gengel v Alex Rybakov | 5-7,1-6 |