| Challenger - Augsburg | 08/20 14:10 | 14 | [416] Daniel Masur v Frantzen, Constantin [98] | 6-3,6-4 | |
| Drummondville, Canada | 11/15 20:45 | 25 | Roko Horvat v Frantzen, Constantin | 7-6,6-1 | |
| Drummondville, Canada | 11/14 15:00 | 19 | Frantzen, Constantin v Smith, Roy | 6-7,6-7 | |
| Drummondville, Canada | 11/13 16:35 | 14 | [474] Omni Kumar v Frantzen, Constantin [207] | 6-2,5-7,5-7 | |
| ITF M25 Harlingen | 10/18 23:30 | 19 | Frantzen, Constantin v Drew Van Orderlain | 3-6,4-6 | |
| Challenger Columbus | 09/18 16:00 | 14 | [283] Frantzen, Constantin v James Trotter [404] | 0-6,2-6 | |
| ITF M25 Marburg | 07/07 10:15 | 26 | Frantzen, Constantin v Milan Welte | 6-3,5-7,1-6 | |
| ITF M25 Marburg | 07/06 10:40 | 25 | Taym Al Azmeh v Frantzen, Constantin | 6-7,1-6 | |
| ITF M25 Marburg | 07/05 09:45 | 54 | Milan Welte v Frantzen, Constantin | 4-6,6-3,5-10 | |
| ITF M25 Marburg | 07/04 11:30 | 54 | Frantzen, Constantin v Daniel Siniakov | 6-4,6-3 | |
| ITF M25 Arlon | 06/22 08:00 | 25 | Frantzen, Constantin v Hoogmartens, Alexander | 4-6,1-6 | |
| ITF M25 Arlon | 06/21 08:00 | 54 | [447] Sandkaulen, Tim v Frantzen, Constantin [423] | 6-1,4-6,8-10 | |
| ITF M25 Arlon | 06/20 10:40 | 54 | Ernaelsteen, Victor v Frantzen, Constantin | 3-6,2-6 | |
| ITF - M15 Meerbusch | 05/02 08:00 | 62 | Frantzen, Constantin v de Rossi, Marco | 3-6,2-6 | |
| ITF - M15 Meerbusch | 05/01 07:30 | 62 | Frantzen, Constantin v Kecojevic, Mihailo | 6-3,6-3 | |
| Split, Singles M-ITF-CRO-05A | 04/25 10:20 | 62 | Drazen Petrovic v Frantzen, Constantin | 6-4,7-5 | |
| ITF - M15 Monastir | 04/06 12:35 | 25 | Frantzen, Constantin v Szymon Kielan | 3-6,5-7 | |
| ITF M25 Monastir | 04/04 13:30 | 62 | Frantzen, Constantin v Katuch, Jakub | 6-3,6-0 | |
| ITF M25 Monastir | 04/04 09:00 | 62 | Frantzen, Constantin v Stubbings, Matthew | 6-1,6-2 | |
| ITF M25 Monastir | 03/27 10:00 | 62 | Frantzen, Constantin v Wattanakul, Pol | 6-7,7-5,8-10 | |
| ITF M25 Monastir | 03/23 07:30 | 62 | Herman, Louis v Frantzen, Constantin | 6-2,6-1 | |
| ITF M25 Monastir | 03/20 09:00 | 62 | Frantzen, Constantin v Alexandre Aubriot | 6-3,6-3 | |
| ITF - M25 Trimbach | 03/17 09:00 | 26 | Haerteis, Johannes v Frantzen, Constantin | 6-3,6-7,6-2 | |
| ITF - M25 Trimbach | 03/16 13:55 | 25 | Frantzen, Constantin v Leonardo Taddia | 6-4,7-5 | |
| ITF - M25 Trimbach | 03/15 09:00 | 54 | Frantzen, Constantin v Laurin Aerne | 3-6,7-6,12-10 | |
| ITF - M25 Trimbach | 03/14 09:00 | 54 | Frantzen, Constantin v Jasin Jakupi | 6-3,6-3 | |
| ITF M25 Glasgow | 02/17 10:00 | 26 | Anton Matusevich v Frantzen, Constantin | 6-4,6-2 | |
| ITF M25 Glasgow | 02/15 10:00 | 25 | Felix Gill v Frantzen, Constantin | 7-6,4-6,0-6 | |
| ITF M25 Glasgow | 02/14 09:55 | 54 | Osgar O'Hoisin v Frantzen, Constantin | 3-6,2-6 | |
| ITF M25 Glasgow | 02/13 11:00 | 54 | Oliver Tarvet v Frantzen, Constantin | Retired |