| ITF Netherlands F6 | 2015/08/25 13:50 | Guy Den Heijer v Johann Willems | 2-6,7-6,6-2 |
| UTR Pro Tennis Series Amsterdam | 2021/11/03 10:30 | Guy Den Heijer v Lawrence Bataljin | 6-0,6-3 |
| UTR Pro Tennis Series Amsterdam | 2021/11/02 10:30 | Guy Den Heijer v Jip Van Assendelft | 6-4,5-2 |
| UTR Pro Tennis Series Amsterdam | 2021/11/01 13:30 | Miko Wassermann v Guy Den Heijer | 2-6,5-7 |
| ITF M15 Girona | 2021/10/19 08:00 | Guy Den Heijer v Vladislav Ivanov | 6-4,6-3 |
| ITF M15 Girona | 2021/10/18 08:00 | Guy Den Heijer v Samir Hamza Reguig | 6-2,6-1 |
| ITF M15 Girona | 2021/10/17 08:00 | Guy Den Heijer v Ervin H Eminefendic | 6-3,6-1 |
| ITF M15 Platja D'Aro | 2021/10/14 14:15 | Jose Fco. Vidal Azorin v Guy Den Heijer | 7-6,1-6,6-2 |
| ITF M15 Platja D'Aro | 2021/10/13 12:00 | Guy Den Heijer v Fermin Tenti | 6-4,3-6,6-1 |
| UTR Pro Tennis Series Amsterdam | 2021/11/04 12:00 | Jip Van Assendelft v Johann Willems | 3-6,2-5 |
| UTR Pro Tennis Series Amsterdam | 2021/11/02 12:00 | Miko Wassermann v Johann Willems | 2-6,2-6 |
| UTR Pro Tennis Series Amsterdam | 2021/11/01 13:30 | Johann Willems v Lawrence Bataljin | 6-1,5-1 |
| UTR Pro Tennis Series Mulheim | 2021/10/17 08:30 | Johann Willems v Christian Hansen | 6-1,5-1 |
| UTR Pro Tennis Series Mulheim | 2021/10/16 08:15 | Constantin Schmitz v Johann Willems | 3-6,1-6 |
| UTR Pro Tennis Series Mulheim | 2021/10/15 11:30 | Eric Vanshelboim v Johann Willems | 2-6,4-6 |
| UTR Pro Tennis Series Mulheim | 2021/10/14 08:30 | Diego Balderas v Johann Willems | 0-6,2-6 |
| UTR Pro Tennis Series Mulheim | 2021/10/12 07:00 | Ivan Marrero Curbelo v Johann Willems | 2-6,3-5 |