Top seed John Isner hammered 26 aces en route to a straight-sets victory over Gilles Muller on Tuesday in the first round of the Memphis Open tennis tournament.

The world No.13, who is chasing his fourth career title, clinched the 7-6 (7-1) 7-6 (7-4) victory by winning the final three points of the second-set tiebreaker.

The 26-year-old Isner won 48 of 50 first-serve points and had just two double faults compared to nine double faults for the Belgian Muller in the 100-minute match.

Isner is also hoping to win his first title indoors. He lost in the 2010 final to fellow American Sam Querrey.

Isner next faces Donald Young who advanced to the second round with a three-set win over Grigor Dimitrov on Monday.

In other matches on Tuesday, Ryan Sweeting beat American countryman James Blake 6-0 6-2 in just 45 minutes and wildcard Querrey rallied to defeat Alejandro Falla 2-6 6-3 6-4.

Sweeting won 75 per cent of his first service points and broke the former world No.4 Blake three times in each set.