Stadium: Court 6 Round: 62 Ground: Clay
| UTR Pro Tennis Series Mulheim | 2021/07/30 13:30 | Guy Den Heijer v Alexander Hoogmartens | 6-2,3-6,4-6 |
| UTR Pro Tennis Series Mulheim | 2021/07/29 13:30 | Mark Wallner v Guy Den Heijer | 2-6,3-6 |
| UTR Pro Tennis Series Mulheim | 2021/07/29 07:00 | Matthew Thomson v Guy Den Heijer | 1-6,3-6 |
| UTR Pro Tennis Series Mulheim | 2021/07/27 09:30 | Billy Harris v Guy Den Heijer | 3-6,2-6 |
| UTR Pro Tennis Series Mulheim | 2021/07/26 11:00 | Guy Den Heijer v Tim Sandkaulen | 7-5,6-3 |
| ITF M25 Marburg | 2021/07/07 10:50 | Aleksandre Metreveli v Guy Den Heijer | 6-3,1-6,6-2 |
| ITF M25 Marburg | 2021/07/06 12:25 | Guy Den Heijer v Florian Broska | 6-3,7-6 |
| ITF M25 Marburg | 2021/07/05 08:00 | Guy Den Heijer v Maximilian Homberg | 6-7,6-2,10-8 |
| ITF M15 Monastir | 2021/07/26 09:00 | Drew Baird v Paulo Knippling | 6-1,6-3 |
| ITF M15 Antalya | 2021/05/30 07:30 | Paulo Knippling v Daniil Savelev | 3-6,1-6 |
| ITF M15 Troisdorf | 2021/05/10 12:30 | Dominik Boehler v Paulo Knippling | 6-0,6-2 |
| ITF M25 Vale Do Lobo | 2021/03/07 12:00 | Paulo Knippling v Angel G Melgar | 3-6,2-6 |
| ITF M25 Vale Do Lobo | 2021/02/22 13:00 | Anthony Genov v Paulo Knippling | 6-3,6-3 |
| Challenger Sao Paulo | 2020/11/21 17:45 | Paulo Knippling v Joao Lucas Reis da Silva | 0-6,1-6 |
| ITF M25 Vale Do Lobo | 2020/10/26 10:30 | Paulo Knippling v Matheus P De Almeida | 1-6,0-6 |
| ITF M15 Troisdorf | 2019/05/06 07:00 | Simon Beaupain v Paulo Knippling | 6-1,6-2 |