Doha, Qatar (SportsNetwork.com) - Former world No. 1 stars Venus Williams and two-time champion Victoria Azarenka posted first-round victories Monday at the Qatar Open tennis event.

The seventh-seeded seven-time Grand Slam champion Williams fought back to beat Aussie Casey Dellacqua 3-6, 6-2, 6-1, while the unseeded two-time major titlist Azarenka upended eighth seed Angelique Kerber of Germany 6-0, 6-3 on the hardcourts at Khalifa International Tennis Complex. Kerber was last year's Doha runner-up to last year's French Open runner-up Simona Halep.

Williams will play her second-round match against Czech Barbora Zahlavova Strycova on Tuesday.

Returning to Doha as a wild card entrant, Azarenka needed just 66 minutes to beat Kerber.

"I'm pretty happy with it. You know, there isn't a lot of things to complain about, but I always try to look at things what I can do maybe better or just stay more consistent," said the former No. 1 who has slipped to 48.

Also on Day 1, Zahlavova Strycova topped German former Wimbledon runner-up Sabine Lisicki 7-5, 6-4, Italian Flavia Pennetta overcame two-time Grand Slam winner and two-time Doha runner-up Svetlana Kuznetsova of Russia 3-6, 6-4, 6-2 and Czech Lucie Safarova dismissed former U.S. Open champ and 2012 Doha runner-up Samantha Stosur 7-6 (7-3), 6-4.

This week's top seeds are Wimbledon champion Petra Kvitova and No. 3 seed, 2011 Doha runner-up and 2014 U.S. Open finalist Caroline Wozniacki. A second-seeded Halep will not defend her title this week after pulling out of the event.

The 2015 Doha titlist will claim $124,000.