Stadium: Court 8 Round: 25 Ground: Clay
| ITF - M15 Vejle | 2021/07/30 14:30 | Jonathan Mridha v Guy Den Ouden | 6-3,6-4 |
| ITF - M15 Vejle | 2021/07/29 16:30 | Guy Den Ouden v Mick Veldheer | 6-4,6-0 |
| ITF - M15 Vejle | 2021/07/28 11:50 | Sebastian Prechtel v Guy Den Ouden | 2-6,2-6 |
| ITF - M15 Esch/Alzette | 2021/07/20 13:00 | Jeffrey Von Der Schulenburg v Guy Den Ouden | 6-4,3-6,7-5 |
| Challenger - Amersfoort | 2021/07/11 14:00 | Guy Den Ouden v Diego Hidalgo | 3-6,6-7 |
| ITF - M25 Marburg | 2021/07/05 12:05 | Yan Sabanin v Guy Den Ouden | 7-6,6-4 |
| ITF - M25 Haga | 2021/06/28 10:15 | Guy Den Ouden v Henri Squire | 2-6,0-6 |
| ITF - M25 Alkmaar | 2021/06/23 10:35 | Deney Wassermann v Guy Den Ouden | 7-6,7-5 |
| ITF - M15 Vejle | 2021/07/29 08:00 | Matias Zukas v Sandro Kopp | 6-3,6-1 |
| ITF - M15 Vejle | 2021/07/27 08:00 | Elmer Moller v Sandro Kopp | 0-6,5-7 |
| ITF - M25 Kottingbrunn | 2021/07/22 08:00 | Giovanni Fonio v Sandro Kopp | 6-1,7-5 |
| ITF - M25 Kottingbrunn | 2021/07/21 12:05 | Taiyo Yamanaka v Sandro Kopp | 1-6,2-6 |
| ITF - M25 Telfs | 2021/07/16 09:30 | Gonzalo Lama v Sandro Kopp | 6-1,6-2 |
| ITF - M25 Telfs | 2021/07/14 08:50 | Francisco Vittar v Sandro Kopp | 2-6,3-6 |
| ITF - M15 Antalya | 2021/05/18 07:00 | Sandro Kopp v Thomas Deschamps | 6-1,5-7,13-15 |
| ITF - M15 Antalya | 2021/05/17 07:00 | Sandro Kopp v Gabriel Roveri Sidney | 6-2,6-3 |