Spanish top seed Carlos Alcaraz abandoned his Rio Open first round match against local favorite Thiago Monteiro on Tuesday due to a right ankle injury.
The two-time grand slam winner rolled his ankle in the opening game of the clash on the Jockey Club Brasileiro's center court.
He initially played on and broke Monteiro's serve, but the Brazilian broke back in the next game.
Alcaraz was in clear discomfort and told the chair umpire he was unable to continue before shaking Monteiro's hand with the score at 1-1.
"I don't know even what to say," Monteiro said. "We didn't want it to be this way."
Alcaraz, who is No. 2 in the world rankings, won the Rio Open in 2022 and finished runner-up at the clay court event last year.
Earlier, former world No. 3 Stan Wawrinka fell to Argentina's Facundo Diaz Acosta 7-5, 6-4.
Others to progress in the ATP 500 tournament on Tuesday included Brazilian Felipe Alves, Dusan Lajovic of Serbia, and Argentine Sebastian Baez.
Uber and Lyft say they'll stay in Minnesota after Legislature passes driver pay compromise
China's space telescopes precisely measure brightest gamma
Industrial chain sharpens China's edge
Xi Focus: Decoding Xi Jinping Thought on Culture Through His Inspection Visit to Jiangxi
Biden says Brown v. Board of Education ruling was about more than education
Foreign automakers buoyed by recovering China mkt
Shanghai industry fair underlines green ways
Ben Whishaw lights up the Croisette as he joins his co
Economy improving, with SOEs poised to lead
Hall of Fame outfielder Ken Griffey Jr. to lead Indianapolis 500 field in Corvette pace car
Images: 2023 World Internet of Things Exposition