World No. 1 Novak Djokovic automatically progressed to the Madrid Open semifinals after his quarterfinal opponent Marin Cilic was forced to withdraw because of food poisoning on Friday.
"Dear fans, Madrid Open organisers, Novak Djokovic, I am sorry to announce that I must withdraw from today's match," said the Croatian on Twitter.
"I have had a terrible night dealing with a case of food poisoning. I am extremely disappointed to have my time in Madrid end in this way. Thank you for the support."
Djokovic, in his 250th week at the top of the men's ATP rankings, will face either Roger Federer or Dominic Thiem in the semifinal on Saturday.
The Serbian, who triumphed in the Spanish capital in 2011 and 2016, beat Taylor Fritz and Jeremy Chardy in the second and third rounds.