Canada's Felix Auger Aliassime returns the ball to Spain's Rafael Nadal during their ATP Madrid Open tennis match at the Caja Magica in Madrid on May 8, 2019. (Photo by Pierre-Philippe MARCOU / AFP via Getty Images)

Canada's Felix Auger Aliassime returns the ball to Spain's Rafael Nadal during their ATP Madrid Open tennis match at the Caja Magica in Madrid on May 8, 2019. (Photo by Pierre-Philippe MARCOU / AFP via Getty Images)

Canada's Felix Auger Aliassime returns the ball to Spain's Rafael Nadal during their ATP Madrid Open round of 32 tennis match at the Caja Magica in Madrid on May 8, 2019. (Photo by Pierre-Philippe MARCOU / AFP via Getty Images)

Canada's Felix Auger Aliassime returns the ball to Spain's Rafael Nadal during their ATP Madrid Open round of 32 tennis match at the Caja Magica in Madrid on May 8, 2019. (Photo by Pierre-Philippe MARCOU / AFP via Getty Images)

Spain's Rafael Nadal serves to Canada's Felix Auger Aliassime during their ATP Madrid Open round of 32 tennis match at the Caja Magica in Madrid on May 8, 2019. (Photo by Pierre-Philippe MARCOU / AFP via Getty Images)

Spain's Rafael Nadal returns the ball to Canada's Felix Auger Aliassime during their ATP Madrid Open round of 32 tennis match at the Caja Magica in Madrid on May 8, 2019. (Photo by Pierre-Philippe MARCOU / AFP via Getty Images)

Spain's Rafael Nadal returns the ball to Canada's Felix Auger Aliassime during their ATP Madrid Open round of 32 tennis match at the Caja Magica in Madrid on May 8, 2019. (Photo by Pierre-Philippe MARCOU / AFP via Getty Images)

Spain's Rafael Nadal serves the ball to Canada's Felix Auger Aliassime during their ATP Madrid Open round of 32 tennis match at the Caja Magica in Madrid on May 8, 2019. (Photo by Pierre-Philippe MARCOU / AFP via Getty Images)