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Makarova broke serve six times and was 15 of 20 on second serve return points in her 52-minute, 6-1, 6-1 triumph over Rybarikova, who came into this week 10-0 at this tournament but has now dropped five straight matches.
"It wasn't as easy as the score indicated," Makarova said. "There were a lot of deuce games, and the points were all long. I'm really happy that I was aggressive, solid and focused."
Makarova had lost her first two encounters with Rybarikova, including a semifinal defeat here last year in which she mustered just two games. She was playing for the first time since her Wimbledon quarterfinal loss to Lucie Safarova.
"Sloane and I hadn't played since the juniors," McHale said. "It was a really tough match, and I'm just happy that I pulled through and advanced to the next round.
"It was a big win for me. I love playing in the US Open Series. This is a good start for me, as I hadn't played a match in a month. It just felt good to be back on the court."
Another WTA Rising Star, Lauren Davis, rallied from a 6-1, 3-1 deficit en route to a 1-6, 6-4, 6-2 win over Peng Shuai in the American's first match since losing to Peng in the third round of Wimbledon.