Stadium: Centre Court Round: 19 Ground: Clay
| Challenger Biel | 2021/09/22 09:00 | Lukas Klein v Mats Moraing | 7-5,4-6,4-6 |
| Challenger Warsaw | 2021/08/28 08:00 | Lukas Klein v Javier Barranco Cosano | 6-3,3-6,4-6 |
| Challenger Warsaw | 2021/08/26 11:00 | Lukas Klein v Andrey Kuznetsov | 7-5,6-1 |
| Challenger Warsaw | 2021/08/24 14:45 | Lukas Klein v Julian Lenz | 6-1,3-6,6-3 |
| Challenger Luedenscheid | 2021/08/17 10:30 | Nicolas Jarry v Lukas Klein | 1-6,7-6,7-6 |
| Challenger Meerbusch | 2021/08/13 11:00 | Lukas Klein v Botic Van De Zandschulp | 4-6,6-3,4-6 |
| Challenger Meerbusch | 2021/08/11 12:00 | Duje Ajdukovic v Lukas Klein | 4-6,6-4,4-6 |
| Challenger Meerbusch | 2021/08/09 14:00 | Lukas Klein v Tobias Kamke | 6-1,6-2 |
| ITF M25 Budapest | 2021/10/03 12:30 | Pawel Juszczak v Mate Valkusz | 3-6,4-6 |
| ITF M25 Budapest | 2021/10/02 12:20 | Mate Valkusz v Fabian Marozsan | 6-3,6-3 |
| ITF M25 Budapest | 2021/10/01 10:00 | Martin Krumich v Mate Valkusz | 2-6,1-6 |
| ITF M25 Budapest | 2021/09/30 09:00 | Milos Karol v Mate Valkusz | 6-7,0-6 |
| ITF M25 Budapest | 2021/09/29 09:20 | Matyas Fuele v Mate Valkusz | 0-6,2-6 |
| Challenger Tulln | 2021/09/06 08:00 | Matteo Martineau v Mate Valkusz | 7-5,1-6,6-4 |
| Challenger Tulln | 2021/09/05 10:25 | Mate Valkusz v Marek Gengel | 6-0,6-1 |
| ITF M15 Bratislava | 2021/08/29 08:00 | Mate Valkusz v Danylo Kalenichenko | 6-0,6-2 |