BRISBANE, Australia — Andy Roddick is surprised when he finds someone who can match him serve for serve, especially when it's an unheralded 22-year-old like Carsten Ball.

The top-seeded Roddick managed only one service break against Ball — the only one of the match — during a 7-6 (0), 6-3 victory Wednesday that sent the American into the quarterfinals of the Brisbane International.

"He serves huge. It was tough for me early on to get a read on it. I expected a tough one today, and it really was," said Roddick, who has one of the biggest serves in tennis. "It's not as much fun when it's flipped."

Justine Henin overcame some service problems in the marquee night match against Sesil Karatantchevato to reach the quarterfinals with a 6-4, 6-3 win in her comeback tournament.

Fourth-seeded Daniela Hantuchova of Slovakia beat Hungary's Agnes Szavay 6-3, 6-1, and Anastasia Pavlyuchenkova of Russia will meet third-seeded Ana Ivanovic in the quarters after ousting Italy's Roberta Vinci 1-6, 6-4, 6-1.

Defending champion Radek Stepanek came from a set and a break down to beat Ukraine qualifier Oleksandr Dolgopolov Jr. 5-7, 7-6 (4), 6-2. The second-seeded Stepanek will face American Wayne Odesnik, a 6-7 (8), 6-2, 6-1 winner over Colombia's Alejandro Falla.

Third-seeded Gael Monfils had a 6-7 (5), 7-6 (5), 6-1 win over fellow Frenchman Florent Serra and will next play American James Blake, who recovered from a break down in the third set and fended off three match points in the tiebreaker to edge Marc Gicquel 6-3, 3-6, 7-6 (6).

"Hard work but a fun result," Blake said. "Sometimes these are the best feelings, to tough it out. I felt like I scrapped and competed really hard."

The former No. 1-ranked Roddick didn't have nearly as much trouble against Ball, who was born in California but plays for Australia.

Roddick, who will play Frenchman Richard Gasquet in the quarterfinals, is playing his first tournament since withdrawing at Shanghai in October with an injured left knee. He's also teaming with Blake in doubles to prepare for the Australian Open.

"I made a lot of returns — think I had four errors with 24 winners," Roddick said. "I served 83 percent first serves — those are numbers you're going to be happy with any day."

Henin dropped her opening service game against Karatantchevato and had to defend powerful groundstrokes from the Kazakhstan qualifier before taking control in the eighth game.

The seven-time Grand Slam champion was serving for the match when she was broken for the third time. Henin broke back immediately, finishing with a forehand winner to advance to a meeting with seventh-seeded Melinda Czink.

Henin attributed the shaky start to the humidity and her first night match in a long time.

"It's only my second match and the fact that I win, and I have an opportunity to play a third match tomorrow in a row, that gives a lot of confidence," Henin said. "I realized on the court it's important I had to be more offensive, and I did when I had to."

Henin beat second-seeded Nadia Petrova on Monday in her first match since May 2008, when she retired while holding the No. 1 ranking.

The 27-year-old Henin announced her comeback in September, soon after Kim Clijsters won the U.S. Open only three tournaments into her own comeback from retirement.

The Belgians could meet in the Brisbane final in what would serve as an intriguing buildup to the year's first major. Clijsters will play a quarterfinal against Lucie Safarova, who had a 6-3, 6-1 win over sixth-seeded Aleksandra Wozniak of Canada on Wednesday.

"I'm reasonable," Henin said, "and I know that it's not only after one match that I'm going to find my rhythm and that I'm going to feel very comfortable on the court."