Updated

CINCINNATI (Reuters) - Former world number one Ana Ivanovic showed flashes of the form that took her to the pinnacle of tennis as she upset ninth seed Victoria Azarenka 2-6 7-6 6-2 in the first round of the Cincinnati Masters on Monday.

Serb Ivanovic, a first-round casualty at San Diego last week, had appeared set for another early exit before rallying to beat the in-form Belarusian, who won the Stanford Classic earlier this month.

The 2008 French Open champion Ivanovic briefly held the world's top ranking that year, but a subsequent collapse in form and a series of niggling injuries have seen her ranking slip to 62nd.

The Serb was joined in the second round by another fallen former top-ranked player in Russia's Dinara Safina, who eased to a 7-5 6-4 win over Italy's Roberta Vinci.

Safina was also forced to dig deep, rallying from 3-5 down in the opening set before closing out her fifth win against the Italian from five matches.

The 24-year-old, now ranked 35 and yet to make a semi-final this season after returning from a back injury that sidelined her for three months, will next face Belgian Kim Clijsters.

Israeli Shahar Peer advanced after Olga Govortsova of Belarus retired when trailing 6-3 4-1, while France's Marion Bartoli thrashed Spain's Anabel Medina Garrigues 6-4 6-0.

Bartoli's compatriot Aravane Rezai was not so fortunate, however, being dumped out by Serb qualifier Bojana Jovanovski 4-6 6-3 6-4.

(Writing by Steve Keating in Toronto; editing by Ian Ransom)