Stadium: Pista 2 Round: 25 Ground: Clay
| Challenger Banja Luka | 2021/09/06 11:55 | Pedja Krstin v Nicolas Moreno De Alboran | 6-2,3-6,6-2 |
| Challenger Barletta | 2021/08/25 09:00 | Pedja Krstin v Mohamed Aziz Dougaz | 2-6,2-6 |
| Challenger Trieste | 2021/07/29 14:50 | Damir Dzumhur v Pedja Krstin | 6-3,6-1 |
| Challenger Trieste | 2021/07/28 08:00 | Pedja Krstin v Viktor Durasovic | 6-3,6-2 |
| Challenger Tampere | 2021/07/21 15:00 | Botic Van De Zandschulp v Pedja Krstin | 6-3,6-1 |
| Challenger Tampere | 2021/07/19 15:30 | JC Aragone v Pedja Krstin | 4-6,4-6 |
| Challenger Jasy | 2021/07/13 07:00 | Pedja Krstin v Dimitar Kuzmanov | 2-6,2-6 |
| ITF M25 Bělehrad | 2021/06/30 11:30 | Pedja Krstin v Bogdan Pavel | 6-1,6-1 |
| Challenger Murcia | 2021/10/01 09:00 | Nicola Kuhn v Flavio Cobolli | 5-7,1-6 |
| Challenger Murcia | 2021/09/29 11:35 | Filip Horanský v Nicola Kuhn | 4-6,6-3,4-6 |
| Challenger Murcia | 2021/09/28 09:00 | Nicola Kuhn v Timofey Skatov | 6-2,6-4 |
| Challenger Szczecin | 2021/09/17 13:00 | Nicola Kuhn v Marco Trungelliti | 6-1,7-5 |
| Challenger Szczecin | 2021/09/16 17:00 | Nicola Kuhn v Alex Rybakov | 6-2,6-2 |
| Challenger Szczecin | 2021/09/14 15:25 | Albert Ramos-Vinolas v Nicola Kuhn | 6-1,4-6,4-6 |
| Challenger Szczecin | 2021/09/13 12:10 | Nicola Kuhn v Matteo Martineau | 6-4,6-1 |
| Challenger Szczecin | 2021/09/12 14:35 | Nicola Kuhn v Nathaniel Lammons | 6-3,6-4 |