Stadium: Pista 2 Round: 26 Ground: Clay
| ATP Monte Carlo MD | 2021/04/14 13:30 | Fognini/Schwartzman v Koolhof/Kubot | 1-6,6-4,10-7 |
| ATP Monte Carlo MD | 2021/04/13 12:55 | Mannarino/Paire v Koolhof/Kubot | 6-7,3-6 |
| ATP Miami MD | 2021/03/25 17:55 | Khachanov/Rublev v Koolhof/Kubot | 6-4,6-2 |
| ATP Dubai MD | 2021/03/17 11:10 | Koolhof/Kubot v Krawietz/Struff | 7-5,3-6,3-10 |
| ATP Dubai MD | 2021/03/15 09:00 | Koolhof/Kubot v Melo/Rojer | 6-4,0-6,12-10 |
| ATP Rotterdam MD | 2021/03/03 13:30 | Chardy/Martin v Koolhof/Kubot | 6-4,6-3 |
| ATP Rotterdam MD | 2021/03/02 10:00 | Mclachlan/Nishikori v Koolhof/Kubot | 5-7,6-3,6-10 |
| Australian Open MD | 2021/02/15 06:55 | Ebden/Smith v Koolhof/Kubot | 7-6,6-4 |