| UTR Pro Tennis Series - Kodaň | 2021/06/20 08:00 | Alexander Konigsfeldt v Warren Sinius | 6-1,6-0 |
| UTR Pro Tennis Series - Kodaň | 2021/06/19 07:00 | Nikolaj Katic v Warren Sinius | 4-5 |
| UTR Pro Tennis Series - Kodaň | 2021/06/18 12:30 | Ludvig Aaes v Warren Sinius | 7-6,6-2 |
| UTR Pro Tennis Series - Kodaň | 2021/06/17 09:30 | Dominik Palan v Warren Sinius | 2-2 |
| UTR Pro Tennis Series - Kodaň | 2021/06/16 11:00 | Philip Hjorth v Warren Sinius | 6-3,6-5 |
| UTR Pro Tennis Series - Kodaň | 2021/06/14 09:30 | Marius Ruzgas v Warren Sinius | 6-2,6-0 |
| UTR Pro Tennis Series Bukurešť | 2021/06/04 11:30 | Warren Sinius v Valentin Vanta | 0-6,2-6 |
| UTR Pro Tennis Series Bukurešť | 2021/06/03 07:30 | Marcelo Zormann v Warren Sinius | 6-0,6-0 |
| ITF M15 Šibenik | 2021/04/19 10:00 | Mehdi Sadaoui v Josip Krstanovic | 7-6,6-4 |
| ITF M15 Šibenik | 2021/04/18 10:00 | Josip Krstanovic v Pavle Daljev | 6-4,6-3 |
| ITF M15 Opatija | 2021/03/21 11:00 | Oleksandr Ovcharenko v Josip Krstanovic | 6-4,6-0 |
| ITF M15 Rovinj | 2021/03/15 11:00 | Josip Krstanovic v Federico Arnaboldi | 1-6,2-6 |
| ITF M15 Rovinj | 2021/03/14 08:30 | Josip Krstanovic v Mattia Frinzi | 6-2,7-6 |
| ITF - M15 Porec | 2021/03/07 12:00 | Damien Wenger v Josip Krstanovic | 7-6,6-0 |
| ITF M15 - Antalya | 2021/02/21 13:00 | Josip Krstanovic v Calin Manda | 2-6,3-6 |
| ITF M15 - Antalya | 2021/01/18 07:00 | Josip Krstanovic v Federico Arnaboldi | 3-6,4-6 |