Memphis, TN (SportsNetwork.com) - It was a good day for American male tennis players Tuesday as five got through the first round of the Memphis Open.

The most notable was sixth-seeded Steve Johnson, who cruised to a 6-3, 6-3 win over lucky loser Filip Krajinovic. Dudi Sela was scheduled to face Johnson but withdrew due to illness.

Sam Querrey, who titled here five years ago, pulled off the biggest upset when he ousted seventh-seeded Benjamin Becker 4-6, 6-2, 6-1.

The other United States natives to advance were qualifiers Ryan Harrison, Denis Kudla and Austin Krajicek.

Day 2's other winners were fifth-seeded Ivo Karlovic and Aussies Bernard Tomic and Sam Groth.

The 6-foot-10 Karlovic smashed 23 aces in getting past Slovak Lukas Lacko 7-6 (9-7), 6-3 at The Racquet Club of Memphis. Karlovic was last year's Memphis runner-up here to Japanese star Kei Nishikori.

This week's top seeds are the U.S. Open runner-up and two-time defending Memphis champ Nishikori, Kevin Anderson and former Memphis runner-up John Isner. Nishikori will face Harrison in the round of 16.

The Memphis champ will earn $106,565.