| UTR Pro Tennis Series - Copenhaga | 2021/10/19 11:30 | Nikolaj Katic v Yurii Dzhavakian | 4-6,4-6 |
| UTR Pro Tennis Series - Copenhaga | 2021/10/18 11:30 | Nikolaj Katic v Henrik Heise Korsgaard | 1-6,6-3,6-4 |
| ITF - M15 Doha | 2021/10/11 13:30 | Boris Butulija v Nikolaj Katic | 6-1,6-3 |
| ITF - M15 Doha - Qualificação | 2021/10/10 15:45 | Theertha Shashank Macherla v Nikolaj Katic | 4-6,6-7 |
| ITF - M15 Doha | 2021/10/04 12:00 | Nikolaj Katic v Tao Mu | 0-6,1-6 |
| ITF - M15 Doha | 2021/10/03 13:20 | Alexey Dubinin v Nikolaj Katic | 2-6,1-6 |
| ITF - M25 Falun | 2021/09/26 11:00 | Nikolaj Katic v Daniel Little | 6-7,4-6 |
| ITF - M25 Jönköping | 2021/09/19 11:00 | Ben Jones v Nikolaj Katic | 6-2,6-7,10-6 |
| UTR Pro Tennis Series - Copenhaga | 2021/10/19 11:30 | Henrik Heise Korsgaard v Vilhelm Fridell | 4-6,6-7 |