The world No.25 went down 3-6 6-4 6-3 to Miomir Kecmanovic in a tick under two hours at the ATP Tour event in Acapulco, Mexico on Monday.

The 21-year-old Australian won the only previous meeting between the pair - that being at the Next Gen ATP Finals in Italy late last year.

After dropping the opening set, the Serb saved all eight break points he faced in the final two sets to triumph and will next play top-seeded Rafael Nadal or his fellow Spaniard, Pablo Andujar.

Stan Wawrinka was forced to dig deep as he saw off USA's Frances Tiafoe 6-3 6-7 (4-7) 7-6 (7-1).

The Swiss third seed sent down 35 aces in the late night thriller which ended just before midnight.

Kyle Edmund built on his recent New York Open title triumph with a win over Feliciano Lopez.

The British number two beat the Spanish veteran 6-4 6-1 to set up a last-16 clash against Australia's Alex Bolt or Canadian Felix Auger-Aliassime.

Adrian Mannarino came from a set down to bring Cameron Norrie's campaign to an early end 2-6 6-3 6-3.

Tommy Paul claimed a hard-fought 6-7 (4-7) 6-4 6-4 victory over Mackenzie McDonald, while another American qualifier in Marcos Giron was a 6-4 7-6 (7-3) winner over local wildcard Gerardo Lopez Villasenor.

Australia's Nick Kyrgios opens his title defence against Frenchman Ugo Humbert on Tuesday, while compatriot John Millman takes on Taylor Fritz.

Australian Associated Press