Stadium: Court 1 Round: 26 Ground: Clay
| ITF M25 Trier | 2021/08/25 11:40 | Mats Rosenkranz v Schmitz, Constantin | 1-6,1-6 |
| ITF M15 Oldenzaal | 2021/08/19 12:35 | Schmitz, Constantin v Johnson, Luke | 7-5,0-6,3-6 |
| ITF M15 Oldenzaal | 2021/08/18 14:10 | Schmitz, Constantin v Eisinga, Zachary | 6-3,7-6 |
| ITF M25 Wetzlar | 2021/08/06 15:55 | Schmitz, Constantin v Peter Heller | 3-6,7-5,1-6 |
| ITF M25 Wetzlar | 2021/08/05 13:55 | Kelly, Dayne v Schmitz, Constantin | 2-6,1-6 |
| ITF M25 Wetzlar | 2021/08/04 12:30 | Schmitz, Constantin v Rother, Jannik | 6-2,6-0 |
| ITF M15 Troisdorf | 2021/05/12 09:00 | Schmitz, Constantin v Kocevar-Desman, Tom | 6-4,4-6,3-6 |
| ITF - M15 Antalya | 2021/04/14 10:30 | Ivan Sergeyev v Schmitz, Constantin | 6-3,5-7,6-3 |
| ITF M25 Trier | 2021/08/25 09:00 | Tom Gentzsch v Ryan Nijboer | 3-6,4-6 |
| ITF M15 Oldenzaal | 2021/08/19 12:45 | Hoogmartens, Alexander v Ryan Nijboer | 1-6,7-5,6-3 |
| ITF M15 Oldenzaal | 2021/08/18 12:45 | Alec Deckers v Ryan Nijboer | 6-3,2-6,4-6 |
| ITF M15 Frederiksberg | 2021/08/05 10:00 | Ryan Nijboer v Hannestad, Benjamin | 1-6,6-4,2-6 |
| ITF M15 Frederiksberg | 2021/08/04 09:25 | Ryan Nijboer v Leyton Rivera | 6-4,6-2 |
| ITF M15 Vejle | 2021/07/28 12:50 | Christian Sigsgaard v Ryan Nijboer | 6-3,6-2 |
| Challenger Amersfoort | 2021/07/13 10:15 | Ryan Nijboer v Johan Nikles | 6-7,2-6 |
| ITF M25 Marburg | 2021/07/10 11:00 | Ryan Nijboer v Nick Hardt | 2-6,4-6 |