Stadium: Center Court Round: 25 Ground: Clay
| ITF Egypt F13 | 2018/04/09 08:30 | Oleg Khotkov v Valentin Guenther | 2-6,6-3,7-6 |
| ITF Egypt F13 | 2018/04/08 08:00 | Cristopher Kohl v Valentin Guenther | 4-6,4-6 |
| ITF Greece F5 | 2018/03/26 07:00 | Valentin Guenther v Gage Brymer | 3-6,3-6 |
| ITF Greece F5 | 2018/03/25 07:00 | Valentin Guenther v Yannick Stephan Born | 6-4,6-2 |
| ITF Greece F5 | 2018/03/24 07:30 | Valentin Guenther v Georgii Kravchenko | 1-6,6-3,6-3 |
| ITF Turkey F7 | 2018/02/18 09:00 | Bogdan Bobrov v Valentin Guenther | 6-7,6-3,6-4 |
| ITF Turkey F7 | 2018/02/17 06:30 | Valentin Guenther v Luca George Tatomir | 6-3,6-1 |
| ITF Switzerland F1 | 2018/02/08 18:40 | Alejandro Davidovich Fokina v Valentin Guenther | 5-7,5-7 |
| ITF Turkey F15 | 2018/04/14 07:30 | Nik Razborsek v Valentin Vanta | 6-1,6-1 |
| Davis Cup | 2018/04/08 13:20 | Nik Razborsek v Altug Celikbilek | 7-5,6-3 |
| ITF Croatia F3 | 2018/03/22 14:00 | Matteo Viola v Nik Razborsek | 7-6,6-3 |
| ITF Croatia F3 | 2018/03/21 10:30 | Tommaso Gabrieli v Nik Razborsek | 3-6,3-6 |
| ITF Croatia F2 | 2018/03/15 09:00 | Zdenek Kolar v Nik Razborsek | 6-7,4-6 |
| ITF Croatia F2 | 2018/03/14 10:35 | Sebastian Prechtel v Nik Razborsek | 1-6,6-4,4-6 |
| ITF Croatia F2 | 2018/03/12 11:00 | Nik Razborsek v Nicolo Crespi | 6-1,6-0 |
| ITF Croatia F2 | 2018/03/11 08:00 | Nik Razborsek v Matteo Fortini | 6-1,6-2 |