NEW YORK -- Serena Williams avenged her major loss to Sloane Stephens, pulling away from the young American for a 6-4, 6-1 win to return to the U.S. Open quarterfinals.

Stephens beat a hobbling Williams in the quarterfinals of the Australian Open in January. But in the rematch Sunday, the 16-time Grand Slam champion served big and controlled points against the 20-year-old.

From 4-4 in the first set, Williams won eight of the last nine games. The 15th-seeded Stephens had 29 unforced errors.

Williams' next match in her title defense is against 18th-seeded Carla Suarez Navarro.

On the men's side, defending champion Andy Murray eased into the U.S. Open's fourth round with a straight-set victory, improving to 29-2 over his past five Grand Slam tournaments.

The third-seeded Murray erased the only two break points he faced and compiled 42 winners while beating 47th-ranked Florian Mayer of Germany 7-6 (2), 6-2, 6-2 Sunday.

In the past 13 months, Britain's Murray won his first two major titles at the U.S. Open last September and Wimbledon this July, and also was a Grand Slam runner-up twice.

His next opponent will be No. 20 Andreas Seppi or Denis Istomin.

Mayer is a two-time Wimbledon quarterfinalist and was trying to reach the U.S. Open's fourth round for the first time. He fell to 1-10 at Grand Slam tournaments against men ranked in the top 10.

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