Stadium: Court 1 Round: 25 Ground: Clay
| Challenger Leon | 2018/04/25 16:00 | Ante Pavic v Darian King | 6-4,6-2 |
| Challenger Leon | 2018/04/23 20:00 | Manuel Sanchez v Darian King | 4-6,6-7 |
| Challenger Guadalajara | 2018/04/20 21:00 | Pedja Krstin v Darian King | 6-2,1-6,6-2 |
| Challenger Guadalajara | 2018/04/18 21:00 | Ante Pavic v Darian King | 3-6,6-2,4-6 |
| Challenger Guadalajara | 2018/04/17 17:00 | Roberto Quiroz v Darian King | 6-3,3-6,3-6 |
| ATP Houston Qual | 2018/04/07 21:15 | Mitchell Krueger v Darian King | 7-5,6-3 |
| Challenger Panama City | 2018/04/03 16:00 | Ante Pavic v Darian King | 6-1,6-4 |
| Challenger Le Gosier | 2018/03/29 18:00 | Dusan Lajovic v Darian King | 6-3,6-4 |
| Challenger Heilbronn Qual | 2018/05/14 11:00 | Miliaan Niesten v Igor Sijsling | 3-6,2-6 |
| Challenger Heilbronn Qual | 2018/05/13 09:00 | Christoph Negritu v Igor Sijsling | 4-6,0-6 |
| Challenger Glasgow | 2018/05/03 09:30 | Igor Sijsling v Roberto Ortega-Olmedo | 6-1,6-7,6-7 |
| Challenger Glasgow | 2018/05/01 09:30 | Bernabe Zapata Miralles v Igor Sijsling | 1-6,3-6 |
| ITF Portugal F8 | 2018/04/17 10:00 | Germain Gigounon v Igor Sijsling | 6-4,6-2 |
| ITF Portugal F7 | 2018/04/12 17:40 | Germain Gigounon v Igor Sijsling | 6-4,6-3 |
| ITF Portugal F7 | 2018/04/12 11:00 | Igor Sijsling v Joao Monteiro | 6-2,6-1 |
| Challenger St Brieuc Qual | 2018/03/26 11:05 | Constant Lestienne v Igor Sijsling | 6-2,5-7,7-6 |