Stadium: Court 3 Round: 26 Ground: Carpet indoor
| 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 |
| ITF M25 Hamburg | 2021/10/23 10:00 | Henri Squire v Johannes Haerteis | 6-4,6-4 |
| ITF M25 Hamburg | 2021/10/22 12:10 | Johannes Haerteis v Daniel Little | 6-4,6-4 |
| ITF M25 Hamburg | 2021/10/21 15:45 | Johannes Haerteis v Leonard Von Hindte | 6-3,6-4 |
| ITF M25 Harlingen | 2021/11/09 15:00 | Noah Schachter v Constantin Frantzen | 7-6,6-2 |
| ITF M25 Fayetteville | 2021/11/02 14:00 | Constantin Frantzen v Mathieu Scaglia | 4-6,5-7 |
| ITF M25 Fayetteville | 2021/11/01 14:00 | Blu Baker v Constantin Frantzen | 7-6,3-6,5-10 |
| ITF M15 Lubbock | 2021/09/26 15:00 | Constantin Frantzen v Sven Lah | 3-6,6-1,4-10 |
| ITF M25 Fort Worth | 2019/10/21 15:00 | Constantin Frantzen v Spencer Papa | 5-7,3-6 |
| ITF M25 Fort Worth | 2019/10/20 15:00 | Constantin Frantzen v Ricardo Alban | 6-3,6-0 |
| ITF M25 Waco | 2019/10/13 15:00 | Constantin Frantzen v Alexander Lebedev | 6-7,2-6 |
| ITF USA F34 | 2018/11/26 21:15 | Michael Geerts v Constantin Frantzen | 6-7,6-2,6-4 |