Switzerland's Belinda Bencic serves the ball to Romania's Simona Halep 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)

Romania's Simona Halep returns the ball to 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)

Romania's Simona Halep serves to 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)

Switzerland's Belinda Bencic returns the ball to Romania's Simona Halep 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)

Switzerland's Belinda Bencic returns the ball to Romania's Simona Halep 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)

Romania's Simona Halep returns the ball to 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)

Switzerland's Belinda Bencic returns the ball to Romania's Simona Halep 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)

Spain's Rafael Nadal celebrates after beating US Frances Tiafoe after their ATP Madrid Open round of 16 tennis match at the Caja Magica in Madrid on May 9, 2019. (Photo by OSCAR DEL POZO / AFP via Getty Images)