Stadium: Court 5 Round: 26 Ground: Clay
| Challenger Alicante MD | 2018/04/06 14:45 | Koolhof W / Sitak A v Andreozzi G / Behar A | 6-3,6-2 |
| Challenger Alicante MD | 2018/04/05 09:30 | Koolhof W / Sitak A v Martinez / Vega | 5-7,6-4,10-5 |
| Challenger Alicante MD | 2018/04/02 12:35 | Koolhof W / Sitak A v Cervantes I / Marrero D | 6-4,6-1 |
| Irving, USA, Doubles | 2018/03/16 23:10 | Petzschner P / Peya A v Koolhof W / Sitak A | 6-4,7-5 |
| Irving, USA, Doubles | 2018/03/15 22:25 | Koolhof W / Sitak A v Krajicek/Lacko | 6-1,6-4 |
| Irving, USA, Doubles | 2018/03/14 19:00 | Inglot/Skupski v Koolhof W / Sitak A | 6-3,1-6,6-10 |
| Sao Paulo, Brazil, Doubles | 2018/03/04 17:20 | Koolhof W / Sitak A v Delbonis F / Gonzalez M | 4-6,2-6 |
| Sao Paulo, Brazil, Doubles | 2018/03/03 20:00 | Berlocq C / Kicker N v Koolhof W / Sitak A | 3-6,3-6 |