Estadio: Court 5 Round: 26 Ground: Clay
| ITF M25 Meerbusch | 2021/04/14 10:30 | Alexander Erler v Marvin Netuschil | 6-3,6-2 |
| ITF M25 Biel | 2021/03/30 08:00 | Alexander Erler v Kilian Feldbausch | 4-6,6-3,5-10 |
| ITF M25 Biel | 2021/03/29 08:00 | Alexander Erler v Mischa Lanz | 6-3,6-4 |
| Challenger Lugano | 2021/03/21 11:50 | Tim Van Rijthoven v Alexander Erler | 7-6,6-0 |
| ITF M25 Trimbach | 2021/03/12 09:55 | Elmar Ejupovic v Alexander Erler | 7-6,6-7,6-3 |
| ITF M25 Trimbach | 2021/03/11 10:00 | Quentin Folliot v Alexander Erler | 4-6,3-6 |
| ITF M25 Trimbach | 2021/03/09 14:40 | Yannik Steinegger v Alexander Erler | 4-6,4-6 |
| ITF M15 Bratislava | 2021/03/03 09:00 | Jurgen Briand v Alexander Erler | 6-7,7-6,7-5 |
| ITF M25 Meerbusch | 2021/04/13 13:30 | Yannick Mertens v Jeroen Vanneste | 6-3,6-4 |
| ITF M15 Monastir | 2021/03/11 08:30 | Yannick Mertens v Naoki Nakagawa | 6-4,3-6,4-6 |
| ITF M15 Monastir | 2021/03/10 10:30 | Yannick Mertens v Constantin Schmitz | 6-0,6-2 |
| ITF M15 Monastir | 2021/02/13 08:30 | Yannick Mertens v Gauthier Onclin | 6-3,1-6,2-6 |
| ITF M15 Monastir | 2021/02/12 10:05 | Yannick Mertens v Juan Bautista Torres | 6-2,6-3 |
| ITF M15 Monastir | 2021/02/11 08:25 | Yannick Mertens v Lukas Mugevicius | 6-1,6-1 |
| ITF M15 Monastir | 2021/02/10 08:30 | Yannick Mertens v Stuart Parker | 5-7,6-4,6-3 |
| ITF M15 Monastir | 2021/02/07 08:30 | Yannick Mertens v Stuart Parker | 3-6,6-4,6-7 |