TORONTO, Canada - Serena Williams defaeted Kirsten Flipkens in the third round of the Rogers Cup on Thursday, family revenge for the Belgian's first round win over Venus Williams a few days earlier.

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Flipkens battled back from a first set blowout to beat Venus, 06 64 62, but the No.13-seeded Belgian couldn't do the same against Serena, falling to the No.1-seeded American and her 10 aces, 60 63.

"After I won the first set I definitely thought about Venus, and I thought about what a good comeback Kirsten had, so I thought, 'I'm not going to get overconfident,'" Williams said. "She's obviously a really good player, so I was just trying to stay really focused as well as really intense at that moment."

Williams was also asked what it's like to have big sister Venus back on the tour alongside her.

"I'm happy she's around," she said. "She's trying to get in the swing of things and play some matches and get more match tough, but it's always good to have her around, and it's good for her to be back."

Williams wasn't the only favorite to move through smoothly later in the day, with No.6 seed and defending champion Petra Kvitova serving up seven aces - and fighting off 10 of the 11 break points against her - in beating No.12 seed and new Carlsbad champion Samantha Stosur in straights, 63 63.

There was a pair of upsets later in the day though, beginning with Sorana Cirstea, who followed up her second round win against No.9 seed Caroline Wozniacki with a 63 64 uspet over No.15 seed Jelena Jankovic, firing a slew of forehand winners late in the match, including five in a row at one point.

"I think I made a huge step forward today by backing up the win from yesterday," Cirstea said. "I think this was one of the issues for me in the past. I would have a good win but then couldn't back it up.

"Now I feel I'm more solid, and I'm taking every match the same and not thinking so much like, 'Oh, I just had a big win.' I'm more like, 'Today is a new day, a new match.' I just have to do the same things I'm doing every single day, and that kind of mentality is helping me. So far it's working here."

Cirstea beating Wozniacki the night before was miraculous in a sense, given she faced match points.

"We always have tough matches, and last night was probably one of the toughest," she said. "I was two match points down and from there on actually I feel like I kind of won the match, because from there I won 15 straight points. I started to take charge and be in control of the points. I feel I really earned that victory yesterday. I fought very hard for it. It was a very good win for me from all areas."

There was another upset later in the day, particularly based on head-to-heads - Dominika Cibulkova snapped a five-match losing streak against Roberta Vinci, winning the first set then fighting off two set points down 5-3 in the second set to close the No.10-seeded Italian out in straights, 63 76(4).