Romania's Simona Halep serves to Netherlands' Kiki Bertens during their WTA Madrid Open final tennis match at the Caja Magica in Madrid on May 11, 2019. (Photo by OSCAR DEL POZO / AFP via Getty Images)

Romania's Simona Halep returns the ball to Netherlands' Kiki Bertens during their WTA Madrid Open final tennis match at the Caja Magica in Madrid on May 11, 2019. (Photo by JAVIER SORIANO / AFP via Getty Images)

Serbia's Novak Djokovic celebrates after defeating Austria's Dominic Thiem during their ATP Madrid Open semi-final tennis match at the Caja Magica in Madrid on May 11, 2019. (Photo by JAVIER SORIANO / AFP via Getty Images)

Serbia's Novak Djokovic serves to Austria's Dominic Thiem during their ATP Madrid Open semi-final tennis match at the Caja Magica in Madrid on May 11, 2019. (Photo by JAVIER SORIANO / AFP via Getty Images)

Austria's Dominic Thiem returns the ball to Serbia's Novak Djokovic during their ATP Madrid Open semi-final tennis match at the Caja Magica in Madrid on May 11, 2019. (Photo by JAVIER SORIANO / AFP via Getty Images)

Switzerland's Roger Federer reacts as he plays against Austria's Dominic Thiem during their ATP Madrid Open quarter-final tennis match at the Caja Magica in Madrid on May 10, 2019. (Photo by GABRIEL BOUYS / AFP via Getty Images)

Switzerland's Roger Federer returns the ball to Austria's Dominic Thiem during their ATP Madrid Open quarter-final tennis match at the Caja Magica in Madrid on May 10, 2019. (Photo by GABRIEL BOUYS / AFP via Getty Images)

Romania's Simona Halep blows a kiss to celebrate defeating Switzerland's Belinda Bencic during their WTA Madrid Open semi-final tennis match at the Caja Magica in Madrid on May 10, 2019. (Photo by GABRIEL BOUYS / AFP via Getty Images)