Koolhof also lost the final battle of a masters tournament three times in 2019, the level below the grand slams. Three years ago, he was also in the final in Miami, together with the Greek Stefanos Tsitsipas.
The Koolhof/Skupski duo is having a good season. They have already won the Melbourne, Adelaide and Doha tournaments this year. They could have taken over the leading position in the annual rankings from Australians Nick Kyrgios and Thanasi Kokkinakis, who won the Australian Open early this year.