John Isner falls, Kevin Anderson advances at Delray Beach

Delray Beach: Australia`s Marinko Matosevic upset US second seed John Isner 6-4, 6-4 Tuesday to reach the second round of the ATP Delray Beach Open.

Isner, who won all three prior meetings with the Bosnian-born Aussie last year, fired 16 aces in a losing cause, surrendering a service break in each set while squandering all three of his own chances in the 75-minute encounter.

Matosevic, ranked 78th and seeking his second ATP final after a 2012 runner-up effort here, booked a second-round date with Japanese qualifier Yoshihito Nishioka, who defeated Dutchman Igor Sijsling 7-5, 6-1.

South African top seed Kevin Anderson ousted Aussie John-Patrick Smith 6-3, 6-3 to book a second-round meeting with Taiwan`s Lu Yen-Hsun, who eliminated Aussie Sam Groth 6-7 (6/8), 7-6 (7/5), 6-4.

Two other Aussies advanced, with Bernard Tomic eliminating Tunisia`s Malek Jaziri 6-3, 6-3 and qualifier Thanasi Kokkinakis downing Serbia`s Filip Krajinovic 6-2, 6-3.

Tomic next faces Serbian eighth seed Viktor Troicki, who outlasted France`s Stephane Robert 6-7 (3/7), 7-5, 6-1, while Kokkinakis will meet Croatian fourth seed Ivo Karlovic.

US sixth seed Sam Querrey was forced to withdraw with a sore back while leading Colombia`s Alejandro Gonzalez 6-3, 1-2.

"I had a sudden movement at the net and kind of jerked my back a little bit," Querrey said.

"It`s an injury that I felt before, but never on a specific motion like this. My lower back just kind of tightened up and I can`t really move it in any direction."

Gonzalez will next face American Donald Young, who followed up his semi-final run from last week in Memphis by defeating Croatia`s Ivan Dodig 7-5, 7-5.

French fifth seed Adrian Mannarino defeated US qualifier Eric Quigley 6-4, 6-4 and faces American wildcard Denis Kudla next.