Stadium: La Foret 4 Round: 14 Ground: Hardcourt indoor
| ITF Great Britain F1 | 2018/02/03 10:00 | Mertens, Yannick v Viola, Matteo | 7-6,6-1 |
| ITF Israel F16 | 2017/12/02 08:30 | Mertens, Yannick v Viola, Matteo | 6-2,6-2 |
| Challenger Biel | 2021/09/20 10:30 | Alexander Ritschard v Mertens, Yannick | 6-2,6-1 |
| Challenger Biel | 2021/09/19 09:30 | Mertens, Yannick v Elmar Ejupovic | 6-3,7-6 |
| ITF M25 Plaisir | 2021/09/16 07:50 | Mertens, Yannick v Tristan Schoolkate | 4-6,6-7 |
| ITF M25 Plaisir | 2021/09/15 09:35 | Mertens, Yannick v Cayre, Paul | 6-4,6-1 |
| 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 |
| Challenger Biel | 2021/09/21 11:25 | Cem Ilkel v Viola, Matteo | 7-6,7-6 |
| Challenger Mallorca | 2021/09/02 19:25 | Frederico Ferreira Silva v Viola, Matteo | 3-6,7-5,6-0 |
| Challenger Mallorca | 2021/09/01 14:00 | Viola, Matteo v Liam Broady | 6-4,3-6,6-4 |
| Challenger - Barletta | 2021/08/24 12:30 | Viola, Matteo v Rodriguez, Cristian | 2-6,5-7 |
| Challenger Verona | 2021/08/17 16:10 | Nerman Fatic v Viola, Matteo | 6-0,6-1 |
| Segovia, Spain | 2021/07/28 10:00 | Viola, Matteo v Benjamin Bonzi | 1-6,2-6 |
| Segovia, Spain | 2021/07/27 08:00 | Mirza Basic v Viola, Matteo | 4-6,1-6 |
| Challenger Pozoblanco | 2021/07/22 17:20 | Viola, Matteo v Emilio Nava | 5-7,6-4,3-6 |