Stadium: Court 4 Round: 44 Ground: Hardcourt indoor
| ITF M25 Plaisir | 2021/09/12 12:30 | Niklas Schell v Max Cunat | 6-4,6-4 |
| ITF M25 Eupen | 2021/09/08 07:30 | Mariano Kestelboim v Niklas Schell | 6-3,6-3 |
| ITF M15 Allershausen | 2021/09/02 08:55 | Mats Rosenkranz v Niklas Schell | 6-3,7-6 |
| ITF M15 Allershausen | 2021/09/01 12:05 | Milan Welte v Niklas Schell | 6-3,2-6,3-6 |
| ITF M25 Ueberlingen | 2021/08/19 10:00 | Niklas Schell v Eduard Esteve Lobato | 6-7,1-6 |
| ITF M25 Ueberlingen | 2021/08/18 09:30 | Niklas Schell v Florian Broska | 3-6,6-3,6-3 |
| ITF M25 Frankfurt am Main | 2021/08/10 10:30 | Taiyo Yamanaka v Niklas Schell | 6-1,6-2 |
| ITF M25 Frankfurt am Main | 2021/08/09 11:55 | Max Wiskandt v Niklas Schell | 6-3,3-6,5-10 |
| ITF M25 Plaisir | 2021/09/12 12:30 | Pierre Antoine Tailleu v Warren Sinius | 6-7,3-6 |
| UTR Pro Tennis Series Sofia | 2021/09/01 06:30 | Valentin Vanta v Warren Sinius | 6-1,5-0 |
| UTR Pro Tennis Series Sofia | 2021/08/31 09:30 | Volodymyr Uzhylovskyi v Warren Sinius | 6-2,5-4 |
| UTR Pro Tennis Series Sofia | 2021/08/30 12:00 | Warren Sinius v George Lazarov | 2-6,2-5 |
| 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 |