Stadium: Court 16 Round: 25 Ground: Hardcourt indoor
| ITF M25 Sintra | 2021/09/08 12:25 | Mertens, Yannick v Felix Corwin | 7-6,3-6,4-6 |
| ITF M25 Bagneres-De-Bigorre | 2021/09/01 11:40 | Mertens, Yannick v Titouan Droguet | 2-6,6-2,3-6 |
| ITF M25 Koksijde | 2021/08/17 16:20 | Mertens, Yannick v Bovy, Arnaud | 7-5,1-6,5-7 |
| ITF M25 Frankfurt am Main | 2021/08/11 14:00 | Mertens, Yannick v Daniel Cukierman | 3-6,3-6 |
| ITF M25 Ajaccio | 2021/07/08 07:00 | Pourroy, Loris v Mertens, Yannick | 6-1,4-6,6-3 |
| ITF M25 Ajaccio | 2021/07/07 10:00 | Pierre Antoine Tailleu v Mertens, Yannick | 4-6,4-6 |
| ITF M25 Bakio | 2021/06/29 15:20 | Mertens, Yannick v Harrison, Christian | 2-6,6-3,4-6 |
| ITF M15 Marbella | 2021/05/30 09:00 | Diego F Flores v Mertens, Yannick | 2-6,1-6 |
| ITF M25 Plaisir | 2021/09/13 14:30 | Oscar Moraing v Cayre, Paul | 3-6,3-6 |
| ITF M25 Plaisir | 2021/09/13 11:55 | Betesh, Jordan v Cayre, Paul | 3-6,1-6 |
| ITF M25 Plaisir | 2021/09/12 14:00 | Edouard Villoslada v Cayre, Paul | 0-6,5-7 |
| UTR Pro Tennis Series Barcelona | 2021/02/07 08:00 | Francois Musitelli v Cayre, Paul | 4-6,4-6 |
| UTR Pro Tennis Series Barcelona | 2021/02/04 10:30 | Vilardo, Francesco v Cayre, Paul | 7-5,6-4 |
| UTR Pro Tennis Series Barcelona | 2021/02/02 13:00 | Andrews, Max v Cayre, Paul | 6-4,5-0 |
| UTR Pro Tennis Series Barcelona | 2021/02/01 09:00 | Cayre, Paul v Nikolas Sanchez Izquierdo | 4-6,4-5 |
| ITF - M15 Bressuire | 2021/01/17 14:00 | Tatlot, Johan Sebastien v Cayre, Paul | 6-4,6-0 |