| ITF M15 Marbella | 2021/05/25 09:00 | Max Alcala Gurri v Mario Mansilla Diez | 6-2,6-4 |
| ITF M15 Valldoreix | 2021/05/09 14:00 | Alvaro Lopez San Martin v Mario Mansilla Diez | 6-3,6-0 |
| ITF M15 Majadahonda | 2021/05/03 12:00 | Arthur Fils v Mario Mansilla Diez | 7-6,6-2 |
| ITF M15 Antalya | 2021/04/04 06:30 | Mario Mansilla Diez v Viacheslav Bielinskyi | 6-2,1-6,4-10 |
| ITF M15 Antalya | 2021/03/28 06:30 | Paul Woerner v Mario Mansilla Diez | 2-6,6-2,11-9 |
| ITF M25 La Nucia | 2021/03/14 08:00 | Carlos Lopez Montagud v Mario Mansilla Diez | 6-2,6-4 |
| ITF M15 La Nucia | 2021/03/09 11:00 | Mario Mansilla Diez v Miguel Damas | 6-3,3-6,3-10 |
| ITF M25 Villena | 2021/01/31 10:30 | Denis Klok v Mario Mansilla Diez | 6-2,6-3 |
| UTR Pro Tennis Series Barcelona | 2021/06/20 07:00 | Ervin H Eminefendic v Alvaro Bueno Gil | 3-6,5-6 |