Stadium: Campo 3 Round: 25 Ground: Clay
| ATP Bělehrad | 2021/04/19 17:00 | John Millman v Danilo Petrovic | 7-5,6-4 |
| Challenger Bělehrad | 2021/04/14 08:45 | Marco Trungelliti v Danilo Petrovic | 6-3,6-2 |
| Challenger Split | 2021/04/09 09:00 | Danilo Petrovic v Andrea Collarini | 2-6,3-6 |
| Challenger Split | 2021/04/07 09:00 | Danilo Petrovic v Maximilian Marterer | 6-1,6-3 |
| Challenger Split | 2021/04/05 12:10 | Danilo Petrovic v Lukáš Rosol | 6-1,6-3 |
| Challenger Marbella | 2021/03/30 15:35 | Danilo Petrovic v Nikola Milojevic | 6-3,3-6,4-6 |
| ATP Miami | 2021/03/22 19:15 | Mischa Zverev v Danilo Petrovic | 7-6,6-2 |
| ATP Acapulco | 2021/03/13 22:30 | Danilo Petrovic v Thiago Seyboth Wild | 3-6,6-4,4-6 |
| Challenger Řím | 2021/04/26 11:15 | Zizou Bergs v Igor Sijsling | 6-7,1-6 |
| Challenger Řím kvalifikace | 2021/04/25 11:05 | Igor Sijsling v Alexey Vatutin | 6-3,6-0 |
| Challenger Bělehrad | 2021/04/11 13:20 | Igor Sijsling v Marco Trungelliti | 3-6,3-6 |
| Challenger Oeiras | 2021/04/02 12:00 | Marco Trungelliti v Igor Sijsling | 6-3,6-4 |
| Challenger Oeiras | 2021/03/31 10:00 | Igor Sijsling v Gian Marco Moroni | 6-2,6-2 |
| Challenger Oeiras | 2021/03/30 09:00 | Manuel Guinard v Igor Sijsling | 1-6,5-7 |
| Challenger Zadar | 2021/03/23 10:45 | Gianluca Mager v Igor Sijsling | 6-4,4-6,6-4 |
| Challenger Petrohrad | 2021/03/09 12:30 | Kacper Zuk v Igor Sijsling | 6-4,6-3 |