| Challenger de Banja Luka | 09/10 08:00 | 24 | [292] Jelle Sels v Guilherme Clezar [403] | 2-6,3-6 | |
| ITF M25 La Marsa | 09/07 09:30 | 28 | [392] Guilherme Clezar v Louis Wessels [366] | 6-1,3-6,3-6 | |
| ITF M25 La Marsa | 09/06 13:00 | 27 | [300] Manuel Guinard v Guilherme Clezar [392] | 3-6,2-6 | |
| ITF M25 La Marsa | 09/05 12:00 | 26 | [463] Michael Geerts v Guilherme Clezar [392] | 5-7,1-6 | |
| ITF M25 La Marsa | 09/03 13:30 | 25 | Pietro Marino v Guilherme Clezar | 1-6,3-6 | |
| ITF M25 Irpin | 08/31 08:00 | 28 | Denis Yevseyev v Guilherme Clezar | 2-6,6-3,6-4 | |
| ITF M25 Irpin | 08/30 08:00 | 27 | [392] Guilherme Clezar v Genaro Alberto Olivieri [492] | 4-6,7-5,6-4 | |
| ITF M25 Irpin | 08/29 08:00 | 26 | Guilherme Clezar v Alexander Weis | 6-2,6-3 | |
| ITF M25 Irpin | 08/28 07:30 | 25 | Guilherme Clezar v Denis Parshutin | 6-0,6-1 | |
| Challenger de L'Aquila | 08/24 16:30 | 27 | [137] Andrej Martin v Guilherme Clezar [431] | 3-6,7-6,6-4 | |
| Challenger de L'Aquila | 08/22 09:40 | 26 | [271] Facundo Mena v Guilherme Clezar [431] | 7-6,4-6,4-6 | |
| Challenger de L'Aquila | 08/21 12:20 | 25 | [431] Guilherme Clezar v Aslan Karatsev [260] | 7-5,6-4 | |
| Challenger de L'Aquila | 08/20 08:00 | 24 | [431] Guilherme Clezar v Ante Pavic [122] | 6-3,6-2 | |
| Challenger de L'Aquila | 08/20 08:00 | 24 | Guilherme Clezar v Ulises Blanch | Cancelled | |
| Challenger de Cordenons | 08/14 18:20 | 25 | [118] Paolo Lorenzi v Guilherme Clezar [359] | 2-6,7-5,7-6 | |
| Challenger de Cordenons | 08/13 08:00 | 24 | [295] Fabien Reboul v Guilherme Clezar [359] | 2-6,2-6 | |
| Challenger de Tampere | 07/25 09:00 | 26 | [304] Guilherme Clezar v Pedja Krstin [244] | 6-7,1-6 | |
| Challenger de Tampere | 07/24 07:30 | 25 | [160] Federico Gaio v Guilherme Clezar [304] | 3-6,5-7 | |
| Challenger de Tampere | 07/22 09:00 | 24 | [304] Guilherme Clezar v Zsombor Piros [362] | 6-3,6-4 | |
| Challenger de Amersfoort | 07/18 09:00 | 26 | [149] Pedro Martinez v Guilherme Clezar [309] | 7-6,6-2 | |
| Challenger de Amersfoort | 07/17 08:00 | 25 | [309] Guilherme Clezar v Tobias Kamke [224] | 6-2,6-2 | |
| Challenger de Amersfoort | 07/15 14:05 | 24 | [296] Frederico Ferreira Silva v Guilherme Clezar [309] | 5-7,1-6 | |
| Challenger de Perugia | 07/11 13:45 | 26 | [262] Gianluigi Quinzi v Guilherme Clezar [322] | 6-3,4-6,7-6 | |
| Challenger de Perugia | 07/10 14:30 | 25 | [322] Guilherme Clezar v Damir Dzumhur [91] | 6-4,3-6,6-4 | |
| Challenger de Perugia | 07/09 08:00 | 24 | [322] Guilherme Clezar v Pavel Kotov [275] | 6-3,3-6,6-3 | |
| Challenger de Perugia | 07/08 09:00 | 166 | [295] Laurynas Grigelis v Guilherme Clezar [322] | 6-4,6-7,1-6 | |
| Challenger de Ludwigshafen | 07/01 16:25 | 24 | [276] Gian Marco Moroni v Guilherme Clezar [322] | 6-3,3-6,7-5 | |
| Challenger de Milán | 06/24 09:00 | 24 | [295] Nino Serdarusic v Guilherme Clezar [321] | 7-6,6-4 | |
| Challenger de Parma | 06/19 08:00 | 25 | [290] Guilherme Clezar v Andrea Pellegrino [356] | 7-5,6-7,4-6 | |
| ATP Lyon | 05/18 10:00 | 64 | [273] Guilherme Clezar v Maxime Janvier [199] | 5-7,6-4,4-6 |