Sam Querrey beat Alejandro Falla for the second time in less than a week, defeating the Colombian 6-3, 6-3 in a first round match at the US National Indoor Championships.
Querrey, who won the Memphis title three years ago, hammered six aces and won 74 percent of his first-serve points as he needed just 58 minutes to eliminate Falla.
Fourth seed Querrey also beat Falla in the quarter-finals of the San Jose tournament on Friday.
Querrey, who is the No. 2 ranked American on the ATP Tour, advances to the second round where he will face the winner of a match between Japan's Go Soeda and Marinko Matosevic of Australia.
Defending champion Jurgen Melzer crashed out of the joint ATP and WTA tournament, losing his opening-round match in straight sets at The Racquet Club of Memphis.
The left-handed Austrian lost to Dutchman Igor Sijsling 6-4, 7-6 (7/3).
Sijsling advanced to a second-round match against Croatian top seed Marin Cilic.
Melzer, who was playing with a broken toe, defeated Milos Raonic in last year's final, snapping the Canadian's win streak at nine straight matches.
In other matches, American veteran James Blake defeated German Florian Mayer 4-6, 6-3, 6-2.
On the women's side, Slovakian seventh seed Magdalena Rybarikova reached the third round by ousting American Lauren Davis 7-6 (7/2), 6-2.
France's Claire Feuerstein upset Czech fifth seed Lucie Hradecka 6-3, 6-4 while German third seed Sabine Lisicki reached the second round with a 7-5, 6-3 victory over American Madison Keys.