MEMPHIS, Tenn. (AP) — Second-seeded Kevin Anderson used a dominant service game to oust Sam Groth 6-3, 6-2 Thursday night in the Memphis Open.

Anderson of South Africa, ranked 15th in the world, won 24 of 25 first-serve points while mixing in a half dozen aces to defeat the Australian in 1 hour.

Fourth-seeded Alexandr Dolgopolov was not as successful in his match, losing 6-1, 7-5 to Bernard Tomic of Australia.

After easily winning the opening set with an accurate serve, Tomic trailed 5-2 in the second set. At 5-3, the 23rd-ranked Dolgopolov failed to serve out the set. Tomic broke the 26-year-old Ukrainian again for a 6-5 lead and held serve in the final game to move to his third quarterfinals of the year.

Also on Thursday, Donald Young advanced with a 7-5, 6-3 victory over qualifier and fellow American Denis Kudla. Steve Johnson of the United States was pushed to a third set tiebreaker by Dustin Brown of Germany before winning 4-6, 7-5, 7-6 (3) in a match that stretched two hours.

In the evening match, Anderson, who received a first-round bye, used early breaks in both sets to contol the match against Groth, ranked 70th in the world. Anderson said he concentrated on holding serve and benefitted from breaks in the fourth game of the first set and the third game of the second.

“He missed a couple of first serves, and I was able to capitalize on some of the second serves,” Anderson said, adding: “It was nice getting those breaks in both sets and pretty early on as well.”

The match featuring a pair of big servers was expected to be closer. Anderson said the tournament’s main court was quicker than ones where he practiced. Realizing the difference, he concentrated more on Groth’s serve.

“It’s always really important to just keep being aggressive,” Anderson said. “As soon as you take a back step, you’re going to put yourself in trouble.”