Stadium: Court 6 Round: 25 Ground: Clay
| ITF M15 Skopje | 2021/06/01 08:00 | Niels Visker v Tom Gentzsch | 6-4,6-1 |
| ITF M15 Skopje | 2021/05/31 08:00 | Niels Visker v Lazar Milicevic | 6-7,6-3,12-10 |
| ITF M15 Valldoreix | 2021/05/13 10:10 | Rayane Roumane v Niels Visker | 6-4,2-6,6-4 |
| ITF M15 Valldoreix | 2021/05/12 08:00 | Georgii Kravchenko v Niels Visker | 6-7,1-6 |
| ITF M15 Valldoreix | 2021/05/11 08:00 | Niels Visker v Francisco Cabral | 7-5,6-0 |
| ITF M15 Valldoreix | 2021/05/10 09:00 | Pierre Delage v Niels Visker | 4-6,2-6 |
| ITF M15 Valldoreix | 2021/05/09 12:00 | Niels Visker v Alejandro Moro Canas | 3-6,6-2,10-6 |
| ITF M15 Majadahonda | 2021/05/06 08:30 | Georgii Kravchenko v Niels Visker | 2-6,6-3,6-2 |
| ITF M25 Vic | 2021/05/19 09:00 | Ryan Nijboer v Facundo Juarez | 6-3,4-6,4-6 |
| ITF M25 Vic | 2021/05/18 08:00 | Laurent Lokoli v Ryan Nijboer | 3-6,4-6 |
| ITF M25 Vic | 2021/05/17 08:00 | Pedro Araujo v Ryan Nijboer | 6-3,0-6,4-10 |
| ITF M25 Vic | 2021/05/16 07:00 | Allan Deschamps v Ryan Nijboer | 7-6,4-6,4-10 |
| ITF M15 Valldoreix | 2021/05/10 09:00 | Francisco Cabral v Ryan Nijboer | 6-1,7-5 |
| ITF M15 Valldoreix | 2021/05/09 13:00 | Matvey Minin v Ryan Nijboer | 6-7,2-6 |
| ITF M15 Majadahonda | 2021/05/03 10:45 | Emilien Voisin v Ryan Nijboer | 5-7,6-2,10-4 |
| ITF M15 Sharm El Sheikh | 2021/04/07 11:15 | Ryan Nijboer v Yuta Shimizu | 2-6,2-6 |