The 19-year-old is seeking to add to his breakthrough victory in Buenos Aires in February.
Fonseca will play Alejandro Davidovich Fokina on Sunday.
The Spaniard was leading 7-6 (7/4), 3-1 when his French opponent Ugo Humbert followed the advice of coach Jeremy Chardy and withdrew with a back injury.
Chardy told Humbert, who had taken a medical time out in the third game and was struggling to serve, to stop if he was in “too much pain”.
“It’s clear you can’t play now,” Chardy said.
© 2025 AFP
