Stadium: Court 9 Round: 24 Ground: Hardcourt outdoor
| Challenger Split | 2021/04/13 13:15 | Lukas Klein v Hugo Gaston | 3-6,6-3,3-6 |
| Challenger Split | 2021/04/12 08:30 | Bozo Barun v Lukas Klein | 1-6,4-6 |
| Challenger Split Qual | 2021/04/11 10:25 | Mats Moraing v Lukas Klein | 6-4,3-6,3-6 |
| Challenger Split | 2021/04/05 10:35 | Lukas Klein v Mirza Basic | 2-6,4-6 |
| Challenger Split | 2021/04/04 13:20 | Lukas Klein v Jerko Brkic | 6-1,6-2 |
| Challenger Zadar | 2021/03/27 10:00 | Lukas Klein v Nikola Milojevic | 4-6,6-4,2-6 |
| Challenger Zadar | 2021/03/26 09:00 | Gianluca Mager v Lukas Klein | 4-6,6-4,4-6 |
| Challenger Zadar | 2021/03/24 10:25 | Lukas Klein v Michael Vrbensky | 5-7,6-3,6-1 |
| ATP Miami | 2021/03/29 01:10 | Alexander Bublik v James Duckworth | 6-4,6-4 |
| ATP Miami | 2021/03/26 15:00 | James Duckworth v David Goffin | 6-3,6-1 |
| ATP Miami | 2021/03/24 18:55 | James Duckworth v Mischa Zverev | 6-2,4-6,6-4 |
| Challenger Cleveland | 2021/03/15 18:15 | James Duckworth v Michael Redlicki | 6-7,1-6 |
| Challenger Biella | 2021/03/09 16:35 | James Duckworth v Andrea Arnaboldi | 4-6,3-6 |
| Challenger Nur-Sultan | 2021/03/05 05:00 | James Duckworth v Prajnesh Gunneswaran | 4-6,6-2,6-7 |
| Challenger Nur-Sultan | 2021/03/04 05:00 | James Duckworth v Vladyslav Manafov | 6-2,6-7,7-5 |
| Challenger Nur-Sultan | 2021/03/03 06:05 | James Duckworth v Alibek Kachmazov | 6-4,5-7,7-5 |