Unheralded Argentine Francisco Comesana recovered from a set down to eliminate top seed Alexander Zverev and reach the semifinals of the ATP 500 Rio Open

Comesana won 71 percent of his first-serve points and converted four of seven break points to prevail in two hours and 31 minutes on the outdoor clay of the Jockey Club Brasileiro.

World No. 2 Zverev had a night to forget, serving four double faults and committing a series of unforced errors as he struggled in the oppressive heat and humidity.

Comesana, who was ranked 86th before the tournament began, will meet Alexandre Muller of France on Saturday with a place in the final at stake.

Earlier, Argentine Camilo Ugo Carabelli progressed to the last four with a 7-6 (5), 6-4 victory over Portugal's Jaime Faria.

Carabelli served eight aces and won 78 percent of points on his first serve to take the match in an hour and 56 minutes.

Carabelli will face countryman and fifth-seeded Sebastian Baez in the semifinals after the latter overcame Tseng Chun-hsin from Chinese Taipei 6-4, 6-1.