| Challenger de Cordenons | 08/13 17:00 | 25 | [236] Guilherme Clezar v Riccardo Balzerani [472] | 6-2,7-5 | |
| Challenger de Pullach | 08/07 16:35 | 25 | [149] Mats Moraing v Guilherme Clezar [221] | 6-2,3-6,6-3 | |
| Challenger de Liberec | 07/30 10:30 | 25 | Goncalo Oliveira v Guilherme Clezar | 7-6,6-2 | |
| Challenger de Praga | 07/27 11:00 | 27 | [264] Aleksandr Nedovyesov v Guilherme Clezar [192] | 6-4,7-6 | |
| Challenger de Praga | 07/26 12:35 | 26 | Guilherme Clezar v Tim Van Rijthoven | 6-3,6-7,6-4 | |
| Challenger de Praga | 07/25 10:40 | 25 | [192] Guilherme Clezar v Daniel Brands [217] | 6-3,6-1 | |
| Wimbledon - Clasificación | 06/25 11:15 | 44 | [129] Thomas Fabbiano v Guilherme Clezar [213] | 6-2,6-3 | |
| Challenger de L'Aquila | 06/23 13:00 | 28 | [190] Facundo Bagnis v Guilherme Clezar [213] | 6-3,5-7,7-6 | |
| Challenger de L'Aquila | 06/22 13:00 | 27 | [213] Guilherme Clezar v Gianluigi Quinzi [216] | 6-3,1-6,7-6 | |
| Challenger de L'Aquila | 06/20 10:05 | 26 | [291] Martin Cuevas v Guilherme Clezar [213] | 3-6,6-1,2-6 | |
| Challenger de L'Aquila | 06/19 10:50 | 25 | [496] Riccardo Bonadio v Guilherme Clezar [213] | 4-6,5-7 | |
| Challenger de L'Aquila | 06/19 08:00 | - | Tommy Robredo v Guilherme Clezar | Cancelled | |
| Challenger Almaty | 06/14 05:00 | 27 | [218] Guilherme Clezar v Yannick Hanfmann [114] | 3-6,2-6 | |
| Challenger Almaty | 06/13 07:55 | 26 | [187] Nikola Milojevic v Guilherme Clezar [218] | 2-6,6-3,1-6 | |
| Challenger Almaty | 06/12 05:20 | 25 | [227] Goncalo Oliveira v Guilherme Clezar [218] | 6-3,3-6,1-6 | |
| Challenger de Shymkent | 06/05 04:00 | 25 | [471] Tung-Lin Wu v Guilherme Clezar [231] | 7-5,6-4 | |
| Challenger de Vicenza | 06/01 14:30 | 27 | [231] Guilherme Clezar v Gian Marco Moroni [295] | 3-6,2-6 | |
| Challenger de Vicenza | 05/31 12:30 | 26 | [231] Guilherme Clezar v Gianluigi Quinzi [204] | 6-4,6-3 | |
| Challenger de Vicenza | 05/30 09:00 | 25 | [125] Lorenzo Sonego v Guilherme Clezar [231] | 6-3,3-6,4-6 | |
| Challenger de Vicenza - Clasificación | 05/28 10:00 | 54 | [351] Gianluca Mager v Guilherme Clezar [231] | 6-3,6-2 | |
| Challenger de Vicenza - Clasificación | 05/27 09:00 | 46 | Luca Giacomini v Guilherme Clezar | 5-7,3-6 | |
| Challenger de Vicenza - Clasificación | 05/26 08:00 | 45 | [397] Fabien Reboul v Guilherme Clezar [231] | 2-6,4-6 | |
| Open de Francia - Clasificación | 05/21 09:15 | 44 | [114] Denis Kudla v Guilherme Clezar [231] | 6-3,6-7,7-5 | |
| Challenger de Savannah | 05/04 15:25 | 27 | [240] Guilherme Clezar v Hugo Dellien [158] | 7-5,4-6,6-7 | |
| Challenger de Savannah | 05/02 14:30 | 26 | [209] Enrique L-Perez v Guilherme Clezar [240] | 6-0,6-7,4-6 | |
| Challenger de Savannah | 04/30 14:00 | 25 | [240] Guilherme Clezar v Dominik Koepfer [243] | 6-2,6-3 | |
| Challenger de Tallahassee | 04/25 17:00 | 26 | [235] Guilherme Clezar v Christian Garin [220] | 4-6,2-6 | |
| Challenger de Tallahassee | 04/24 18:55 | 25 | [235] Guilherme Clezar v Andrea Arnaboldi [234] | 6-2,6-4 | |
| Challenger de Sarasota | 04/20 16:00 | 27 | [241] Guilherme Clezar v Reilly Opelka [211] | 7-5,4-6,4-6 | |
| Challenger de Sarasota | 04/19 15:40 | 26 | [241] Guilherme Clezar v Evan King [192] | 7-6,3-6,6-2 |