Cornet won 6-2, 7-5 and will face Austrian wild card Patricia Mayr, who upset No. 7-seeded Tathiana Garbin of Italy 6-3, 6-4.

The 35th-ranked Petkovic broke early for a 2-0 lead before losing the next six games to drop the first set. She then served for the second set at 5-3, but was broken when she double-faulted and lost her next service game as well to slip to defeat.

Cornet, who also reached the last eight in Budapest earlier this month, saved seven of nine break points.

Garbin broke Mayr in the opening game but lost serve twice before dropping the first set. The 123rd-ranked Mayr, who has won 10 titles on the lower-ranked ITF circuit, closed out the match on her first match point.

Julia Goerges of Germany also advanced by defeating Mariya Koryttseva of Ukraine 6-2, 7-5. Goerges, who reached the semifinals in Palermo last week, will play Russia's Anastasia Pivovarova in the last eight.

Yvonne Meusburger of Austria reached the quarterfinals for a fourth straight year by defeating 2008 finalist Lucie Hradecka of Czech Republic 7-5, 7-5.

Meusburger will play eighth-seeded Anastasija Sevastova of Latvia for a place in the semifinals.

In Hamburg, Germany, Juan Carlos Ferrero of Spain defeated Jarkko Nieminen of Finland 6-2, 3-6, 6-4 to reach the quarterfinals of the German Open for the first time in nine years.

Ferrero reached the final of the clay-court tournament in 2001 but hasn't been past the third round here in his other five attempts.

Florian Mayer of Germany made the last eight by dispatching Maximo Gonzalez of Argentina 7-6 (1), 6-0.

In other matches Thursday, Andreas Seppi edged Fabio Fognini 6-4, 6-4, and Potito Starace rallied past qualifier Pere Riba 4-6, 6-4, 6-4.

In Johns Creek, Georgia, John Isner did what he does best - pull out a long tennis match.

Isner, the No. 2 seed, fought through another final-set tiebreaker with a 4-6, 7-6 (6), 7-6 (7) victory over Gilles Muller of Luxembourg in the second round of the Atlanta Tennis Championships on Wednesday night.

"I was able to play well when I needed to early in the second set, and the crowd would pump me up when I'd get down 15-40," he said. "I just didn't want to let them down. I didn't want to lose my first match here." Isner, who became a household tennis name after winning a three-day, 183-game match at Wimbledon last month, improved to 16-5 in career final set tiebreakers.

He had not played since losing in the second round at Wimbledon the day after his record win over Nicolas Mahut of France.

"With Gio as my opponent, he's probably one of the last guys I want to play," Isner said. "First match back (against) a big-serving left-hander, he's not going to give you much rhythm. So that was a little bit working against me, but I just told myself to compete." Michael Russell will face Isner in the quarterfinals on Friday night.