Italy's Gianluca Mager hits the ball during a quarter-final match against Austria's Dominic Thiem during the ATP World Tour Rio Open 2020 tournament, Jockey Club in Rio de Janeiro, Brazil in the early hours of Feb 22, 2020. (MAURO PIMENTEL / AFP)

RIO DE JANEIRO - Italian qualifier Gianluca Mager beat Austrian top-seed Dominic Thiem 7-6 (4), 7-5 on Saturday to advance to the Rio Open semifinals in a rain-interrupted match.

Gianluca Mager will confront Hungary's Attila Balazs for a place in the final of South America's only ATP 500 event

World No 128 Mager led 7-6, 2-1 when play was called off late on Friday because of heavy rain at the Jockey Club Brasileiro.

Mager held his nerve upon the resumption of play and sent down an ace on his first match point to secure an unexpected victory in one hour and 55 minutes.

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"It's unbelievable," said Mager. "For me, it was a dream only to play with him. Now that I beat him, for me, it is a dream. He is a great, unbelievable player... I am very emotional."

Mager will confront Hungary's Attila Balazs for a place in the final of South America's only ATP 500 event.

Chile's Cristian Garin and Borna Coric were due to meet in the other semifinal, which was delayed on Saturday because of rain.