FP – Bernard Tomic and Thanasi Kokkinakis have won through to the second round of the Delray Beach ATP event in Florida, but a typically powerful serving display from fellow Australian Sam Groth wasn’t enough.

Tomic, who reached the quarter-finals of the Memphis Open last week, outclassed Tunisia’s Malek Jaziri 6-3 6-3 in his opening match on Tuesday.

Kokkinakis was too strong for Serbian Filip Krajinovic in a 6-2 6-3 victory at the hard-court tournament.

Groth slammed down 15 aces but went down 6-7 (6-8) 7-6 (7-5) 6-4 to Taiwan’s Yen-Hsun Lu.

Meanwhile, South African top seed Kevin Anderson and US second seed John Isner were each set to open in night matches against Australians – Anderson facing John-Patrick Smith and Isner meeting Marinko Matosevic.

US sixth seed Sam Querrey was forced to withdraw with a sore back while leading his first-round match 6-3 1-2 against Colombia’s Alejandro Gonzalez.

“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, whose hot streak of form – he reached the semi-finals in Memphis – continued with a 7-5 7-5 defeat of Croatia’s Ivan Dodig.

French fifth seed Adrian Mannarino defeated US qualifier Eric Quigley 6-4 6-4 while US seventh seed Steve Johnson advanced 6-3 4-1 when Kazakstan’s Mikhail Kukushkin retired due to illness and Serbian eighth seed Viktor Troicki outlasted France’s Stephane Robert 6-7 (3-7) 7-5 6-1.