Stadium: Court 2 Round: 25 Ground: Clay
| ITF M25 Telfs | 2021/07/11 09:00 | Katuch, Jakub v Niklas Waldner | 1-6,3-6 |
| ITF M25 Most | 2021/05/24 09:00 | Niklas Waldner v Hubner, Edward | 4-6,3-6 |
| ITF M25 Most | 2021/05/23 08:00 | Niklas Waldner v Milos Karol | 3-6,7-5,10-3 |
| ITF - M15 Monastir | 2021/05/09 11:00 | Taisei Ichikawa v Niklas Waldner | 6-1,6-0 |
| ITF - M15 Monastir | 2021/05/02 12:00 | Andrea Picchione v Niklas Waldner | 6-2,6-4 |
| ITF - M15 Monastir | 2021/04/25 11:30 | Niklas Waldner v Vasa, Iiro | 1-6,4-6 |
| ITF M15 Anif | 2020/08/23 07:00 | Galoppini, Davide v Niklas Waldner | 6-3,6-4 |
| Vogau, Singles Qualifying M-ITF-AUT-04A | 2020/08/17 11:30 | Niklas Waldner v Alexander Shevchenko | 4-6,2-6 |
| Iasi, Romania | 2021/07/13 12:15 | Zdenek Kolar v David Poljak | 6-2,7-5 |
| Iasi, Romania | 2021/07/12 08:00 | Vlad Andrei Dancu v David Poljak | 2-6,0-6 |
| Iasi, Romania | 2021/07/11 09:20 | Mircea-Alexandru Jecan v David Poljak | 4-6,0-6 |
| ITF M25 Wroclaw | 2021/06/29 13:25 | Ignatik, Uladzimir v David Poljak | 6-0,6-2 |
| ITF M15 Bergamo | 2021/06/22 15:50 | David Poljak v Dali Blanch | 2-6,6-3,3-6 |
| Prostejov, Czech Republic | 2021/06/15 09:35 | Alex Molcan v David Poljak | 6-3,6-3 |
| Prostejov, Czech Republic | 2021/06/14 08:30 | Haerteis, Johannes v David Poljak | 5-7,3-6 |
| Prostejov, Czech Republic | 2021/06/13 09:00 | David Poljak v Verbeek, Sem | 6-3,6-3 |