Juan Martin del Potro dispatched Jeremy Chardy with minimum fuss to make the last 16 at the Delray Beach Open in Florida on Tuesday.
The Argentine second seed broke serve four times on the way to a 6-2, 6-4 win over the Frenchman and will now play young American Frances Tiafoe.
Meanwhile, sixth-seeded American John Isner overcame a slow start to beat Macedonia’s Radu Albot in three sets.
Isner gained revenge after losing to Albot in the first round of last week’s New York Open, but bounced back after losing the first set to triumph 5-7, 6-3, 6-4, for is first win in four matches.
Fourth seed American Sam Querrey was the surprise of the day, losing to young compatriot Taylor Fritz in a deciding set tie-breaker 2-6, 6-3, 7-6 (7-4).
— Delray Beach Open (@DelrayBeachOpen) February 21, 2018
In other action, former world number three Milos Raonic, a runner-up here last year to champion Jack Sock, continued his comeback from injury with a straight sets win over Japan’s Taro Daniel 6-1, 7-5.
Raonic will meet America’s Steve Johnson in the next round after he defeated Georgia’s Nikoloz Basilashvili 6-3, 6-4.
The 2015 champion Ivo Karlovic was another early casualty, missing 11 out of 12 break points as he crashed out to 18-year old Canadian Denis Shapovalov.