Murray - who joined Roger Federer, Novak Djokovic, Andre Agassi and Rafael Nadal in the 500 club - said in a post-match interview that he "probably (doesn't) have too long left but I'll do the best that I can these last few months," a possible hint that the 36-year-old is considering retirement.
Second seed Andrey Rublev of Russia rallied past China's Zhizhen Zhang 6-7, 6-2, 6-4, while Polish third seed Hubert Hurkacz outlasted German Jan-Lennard Struff 7-6, 6-7, 7-6.
Seventh seed Alexander Bublik also needed three sets to top Czech qualifier Tomas Machac 2-6, 6-3, 7-6, and Dutchman Botic van de Zandschulp upset sixth seed Adrian Mannarino 7-6, 7-5.
American Sebastian Korda knocked off Russia's Pavel Kotov 6-0, 6-2 in 54 minutes, and Tallon Griekspoor of the Netherlands led 7-5, 2-0 when Jordanian opponent Abdullah Shelbayh retired.
Acapulco
Two seeded US players lost their first-round matches at Acapulco, Mexico. Great Britain's Jack Draper needed just 86 minutes to oust seventh-seeded Tommy Paul of the United States 6-0, 6-4, and Italy's Matteo Arnaldi stunned fourth-seeded Taylor Fritz 6-4, 4-6, 6-3.
Draper never dropped his serve, shaking off three break points while converting four of his five break opportunities. Arnaldi wound up with a 39-22 edge in winners in his match, while he and Fritz each committed 16 unforced errors.
Third-seeded Alex De Minaur sailed into the second round with a 6-2, 6-1 blowout of Japan's Taro Daniel. Ben Shelton rallied past Dan Evans 2-6, 7-5, 7-6, and Serbia's Miomir Kecmanovic came from behind to defeat Diego Schwartzman 4-6, 6-3, 6-1. Austria's Sebastian Ofner edged Mexico's Ernesto Escobedo 6-7, 6-4, 7-6.
In late matches, Japan's Yoshihito Nishioka beat Portugal's Nuno Borges 3-6, 6-2, 6-4, and Italy's Flavio Cobolli eliminated Canada's Felix Auger-Aliassime 2-6, 6-3, 6-2.
Santiago
Sixth-seeded Facundo Diaz Acosta prevailed in an all-Argentine first round, rallying past Pedro Cachin 5-7, 6-3, 7-6 on clay at Santiago, Chile.
In a match that lasted three hours, and eight minutes, Diaz Acosta won the last five points of the third-set tiebreaker. Cachin had 18 break chances in the match but converted just three of them.
Another Argentine, Federico Coria, registered a 6-1, 7-6 win over Slovakia's Alex Molcan. French qualifier Corentin Moutet upset seventh-seeded Roberto Carballes Baena 6-3, 7-5, 6-2, and Spain's Pedro Martinez got past Italy's Francesco Passaro 6-4, 6-1.
