Stadium: Court 1 Round: 62 Ground: Clay
| ITF Germany F10 Qual | 2018/07/29 13:30 | Mats Rosenkranz v Breitbach, Kai | 6-1,4-6,3-6 |
| ITF Germany F5 | 2018/06/24 10:00 | Hoffmann, Bjorn v Breitbach, Kai | 5-7,6-7 |
| ITF USA F33 Qual | 2017/10/08 16:30 | Breitbach, Kai v Johnson, Trevor Allen | 3-6,1-6 |
| Meerbusch, Allemagne, Qualifications | 2017/08/13 14:10 | Breitbach, Kai v Gabb, Richard | 1-6,5-7 |
| Meerbusch, Allemagne, Qualifications | 2017/08/12 15:40 | Anton Chekhov v Breitbach, Kai | 6-3,2-6,6-7 |
| Meerbusch, Allemagne, Qualifications | 2016/08/13 09:45 | Niklas Schell v Breitbach, Kai | 6-3,7-6 |
| ITF Germany F2 Qual | 2016/01/18 09:00 | Alexander Bublik v Breitbach, Kai | 6-4,6-4 |
| ITF Germany F3 Qual | 2015/01/18 12:30 | Breitbach, Kai v Mazzella, Manuel | 0-6,4-6 |
| ITF Germany F10 Qual | 2018/07/29 13:30 | Muzzi, Felipe v Schmitz, Constantin | 0-6,0-6 |
| ITF Germany F9 | 2018/07/25 16:00 | Boehler, Dominik v Schmitz, Constantin | 6-1,6-3 |
| ITF Germany F9 | 2018/07/24 17:30 | Botezan, George v Schmitz, Constantin | 2-6,7-5,3-6 |
| ITF Germany F9 | 2018/07/23 10:00 | Seraphim, Christian v Schmitz, Constantin | 3-6,4-6 |
| ITF Germany F9 | 2018/07/22 08:00 | Schmitz, Constantin v Chaukulkar, Tejas | 6-3,6-1 |
| ITF USA F37 | 2017/11/14 16:00 | Schmitz, Constantin v Nuno Borges | 1-6,7-6,2-6 |
| ITF USA F36 | 2016/11/13 16:00 | Schmitz, Constantin v Mina, Gianni | 6-4,1-6,0-6 |
| ITF USA F36 | 2016/11/12 19:00 | Schmitz, Constantin v Rubin Statham | 6-3,2-6,7-6 |