Netherlands' Kiki Bertens returns the ball to Romania's Simona Halep 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)

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)

Austria's Dominic Thiem celebrates after winning a point against 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)

Serbia's Novak Djokovic returns the ball 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)

Serbia's Novak Djokovic returns the ball 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 reacts after winning a point against 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)

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)