Top seed David Ferrer eased through to the second round of the ATP Abierto Mexicano Telcel with a straight-sets victory over John Millman.
Ferrer, the reigning champion, needed just one hour and 22 minutes to get past his Australian opponent 6-4, 6-2.
The Spaniard broke five times during the match and saved two break points in a commanding performance as he pursues a fifth title at the hard-court event.
Ferrer will meet Alexandr Dolgopolov in the last 16 after the Ukrainian defeated Steve Johnson 7-5, 7-6 (7-4).
In the day’s big upset, former US Open champion Marin Cilic crashed out of the tournament after losing in three sets against qualifier Ryan Harrison, who sits 120 places below him in the world rankings.
Harrison won a staggering 83 per cent of points from his first serve while Cilic struggled with his second serve throughout the 3-6, 6-3, 2-6 loss.
Rising teenager Taylor Fritz upset number eight seed Jeremy Chardy 6-4, 3-6, 6-3.
Fritz withstood 12 aces from the Frenchman but was more effective on break points, landing four of his five opportunities.
Elsewhere there were straight set victories for Dominic Thiem, Bernard Tomic, Sam Querrey and Grigor Dimitrov over Damir Dzumhur, Rajeev Ram, Dudi Sela and Denis Kudla respectively.
While Russian Dimitry Tursunov had a narrow 6-4, 3-6, 7-5 win over Sam Groth in just under two hours and Aljaz Bedene advanced after Croat Ivo Karlovic retired at the 48-minute mark.