Second-seeded Casper Ruud of Norway pulled out of the Rio Open clay-court tournament with an abdominal injury.
Ruud told a news conference that he was still feeling the effects of an injury he picked up during Sunday's final of the Argentina Open, which he won.
“I tried as much as I could, but unfortunatelly it wasn't possible,” Ruud said.
“It was a tough decision, I was looking forward to play here.”
Ruud was replaced by Spain's Roberto Carballes Baena, who lost his second-round match against Argentina's Francisco Cerundolo 6-3, 6-2 after the second set was halted for a rain delay.
Cerundolo will next face Serbia's Miomir Kecmanovic, who beat sixth-seeded Lorenzo Sonego of Italy 7-5, 6-4.
Rain came back to Rio late on Thursday and forced the suspension of the two remaining matches of the day.
Seventh seed Carlos Alcaraz of Spain was beating Argentina's Federico Delbonis 5-4 when play was stopped.
The encounter will take place Friday.
Also on Friday, top-seeded Matteo Berrettini of Italy will play Brazil's Thiago Monteiro.
- Reported by AP
