Stadium: Court 2 Round: 25 Ground: Hardcourt outdoor
| Challenger Manama | 2021/11/22 08:00 | Johannes Haerteis v Alexandar Lazarov | 3-6,6-7 |
| Challenger Manama | 2021/11/21 10:05 | Johannes Haerteis v Ammar Faleh Alhogbani | 6-2,6-1 |
| Challenger - Helsinki | 2021/11/14 09:00 | Johannes Haerteis v Viktor Durasovic | 4-6,6-7 |
| Challenger - Eckental | 2021/11/02 18:15 | Maxime Cressy v Johannes Haerteis | 6-7,6-4,6-3 |
| Challenger - Eckental | 2021/11/01 11:15 | Johannes Haerteis v Uladzimir Ignatik | 4-6,6-2,7-6 |
| Challenger - Eckental | 2021/10/31 13:30 | Lucas Miedler v Johannes Haerteis | 3-6,7-5,3-6 |
| Challenger Ismaning | 2021/10/25 11:50 | Otto Virtanen v Johannes Haerteis | 4-6,6-3,6-3 |
| Challenger Ismaning | 2021/10/24 12:35 | Johannes Haerteis v Tristan Lamasine | 6-4,6-4 |
| Challenger - Eckental | 2021/11/02 13:15 | Henri Squire v Alexander Erler | 7-6,2-6,7-6 |
| Challenger - Eckental | 2021/11/01 10:00 | Alexander Erler v Henri Squire | 4-6,2-6 |
| Challenger - Eckental | 2021/10/31 10:35 | Alexander Erler v Artem Dubrivnyy | 6-1,6-3 |
| ATP - Wenen | 2021/10/23 09:00 | Alexander Erler v Gianluca Mager | 7-6,2-6,4-6 |
| Challenger - Boekarest | 2021/09/20 11:20 | Vitaliy Sachko v Alexander Erler | 6-2,6-2 |
| Challenger - Tulln | 2021/09/06 12:10 | Alexander Erler v Lukas Rosol | 4-6,7-5,1-6 |
| Challenger - Como | 2021/08/31 08:00 | Riccardo Bonadio v Alexander Erler | 3-6,6-3,6-3 |
| Challenger - Como | 2021/08/30 09:00 | Filippo Baldi v Alexander Erler | 6-7,4-6 |