| UTR Pro Tennis Series Zadar | 2021/07/04 07:00 | Bozo Barun v Warren Sinius | 6-1,6-0 |
| UTR Pro Tennis Series Zadar | 2021/07/01 09:30 | Warren Sinius v Jerko Brkic | 6-3,6-5 |
| UTR Pro Tennis Series Zadar | 2021/06/30 08:00 | Warren Sinius v Constant De La Bassetiere | 3-6,6-6 |
| UTR Pro Tennis Series Zadar | 2021/06/29 11:00 | Warren Sinius v Frane Nincevic | 5-7,3-6 |
| UTR Pro Tennis Series Zadar | 2021/06/28 12:30 | Warren Sinius v Josip Krstanovic | 2-6,1-5 |
| UTR Pro Tennis Series Copenhagen | 2021/06/20 08:00 | Alexander Konigsfeldt v Warren Sinius | 6-1,6-0 |
| UTR Pro Tennis Series Copenhagen | 2021/06/19 07:00 | Nikolaj Katic v Warren Sinius | 4-5 |
| UTR Pro Tennis Series Copenhagen | 2021/06/18 12:30 | Ludvig Aaes v Warren Sinius | 7-6,6-2 |
| UTR Pro Tennis Series Sofia | 2021/08/29 12:00 | George Lazarov v Mario Radev | 6-0,6-1 |