Schwartzman, the No.1 seed in Buenos Aires, needed three hours, 41 minutes to edge Pablo Cuevas 5-7 7-6 (13-11) 7-5 in an epic battle at the ATP 250 tournament.

The Argentinian, last year's runner-up, saved four match points in the second set before overcoming Cuevas.

Schwartzman managed two breaks of serve in the deciding set, including the decisive one in the 12th game.

Awaiting him in the semi-finals is Pedro Sousa, the lucky loser continuing his run with a 7-6 (7-5) 6-4 victory over Thiago Monteiro.

Casper Ruud will face Juan Ignacio Londero in the other semi-final after their respective wins over Dusan Lajovic and Guido Pella.

At the New York Open, Opelka's title defence came to an end with a 5-7 6-4 6-4 loss to qualifier Jason Jung.

Opelka served 24 aces, but the 2019 champion was broken twice to fall to defeat in one hour, 52 minutes.

Jung will meet Andreas Seppi in a semi-final after the Italian veteran got past Australia's Jordan Thompson 6-7 (2-7) 6-4 6-1.

Kyle Edmund advanced thanks to a 3-6 6-2 7-6 (7-5) win against Kwon Soon-woo, while Miomir Kecmanovic beat Ugo Humbert 3-6 6-2 6-4.