Ana Ivanovic upset the seedings in a battle of former French Open champions with Francesca Schiavone at the Dubai Open on Tuesday, insisting afterward that there is still another Grand Slam title left in her.

The 2008 Roland Garros champion from Serbia beat the 2010 champion from Italy 6-1, 7-5 with a first-round performance that belied her relative decline over the past three years.

Marion Bartoli was another heavyweight to fall, the No.6 seed from France being beaten 6-4, 6-3 by China's Peng Shuai.

Bartoli retired with a calf problem after one set in Saturday's semifinals in Doha and after this time taking 3-0 leads in both sets, she slowed markedly, and ended the match limping.

Peng next plays Daniela Hantuchova. Ivanovic, meanwhile, faces Russia's Maria Kirilenko, who is suffering from a neck injury, and has a chance of earning a quarterfinal meeting with defending champion Caroline Wozniacki.

Ivanovic hurtled so quickly into a 5-0 lead, with such forceful blows from her first serve and forehand, that it seemed unlikely that she would be troubled.

But Schiavone summoned a typically tenacious second-set performance, twice recovering from dropped service games and threatening to do that a third time before Ivanovic closed the match out in a tight finish.

"I believe I can get back to the top and win a Grand Slam again - that's why I am here," said Ivanovic. "If that wasn't going to happen or I didn't feel that it could, I wouldn't be here.

"It's strange that at the age of 24 I am considered old. It's a great challenge for us players who have been around for a while," she said, referring to the rise during 2011 of Victoria Azarenka, Petra Kvitova, and Caroline Wozniacki.

"They are pushing us to get better and I still believe that I can."

Ivanovic was also pleased with the way in which she handled a finish in which her English coach Nigel Sears unexpectedly appeared on court before she could serve for the match for a second time.

Asked why she had called for him, Ivanovic said, "I didn't - he just stood up and came! He said, 'You are doing a good job, just keep at it.'

"I tried not to think about the scores. I tried to stay aggressive and also to mix it up. I tried very hard to do that."

Earlier, fifth seed Agnieszka Radwanska from Poland narrowly survived.

She was 3-5 down in the final set against Canadian qualifier Aleksandra Wozniak before escaping 6-1, 6-7 (6/8), 7-5.