NEW YORK (AP) Li Na looked like a Grand Slam champion, while Laura Robson looked like a promising teenager.
The fifth-seeded Li avenged her third-round upset loss to the young Brit at last year's U.S. Open, winning in straight sets Friday at the same stage at Flushing Meadows.
Li, the 2011 French Open champ, rallied from down a break in the second set for a 6-2, 7-5 victory. A year ago, Robson's upset of Li was the biggest victory of her breakthrough run. Meanwhile, it was the third straight frustrating U.S. Open loss for the Chinese star.
Robson was ranked 89th coming into last year's tournament. She had never advanced past the second round at a Grand Slam event or defeated a top-10 opponent.
That all changed when she upset major champions Kim Clijsters and Li back-to-back to make the fourth round. Now 19, Robson was seeded 30th at Flushing Meadows and coming off a fourth-round run at Wimbledon.
But on Friday, she had 30 unforced errors to seven winners.
Li is back in the fourth round at the U.S. Open for the first time since 2009. She had 11 aces Friday - including one on a second serve on match point - and won all nine points when she went to the net.
Agnieszka Radwanska needed nearly two hours to slip past No. 32-seeded Anastasia Pavlyuchenkova 6-4, 7-6 (1). The third-seeded Pole faced 10 break points, but Pavlyuchenkova was able to convert only two, while Radwanska was 3 for 5.
Serena Williams will be back on court later Friday a day after playing singles and doubles, facing Yaroslava Shvedova in the nightcap at Arthur Ashe Stadium.
Former champs Novak Djokovic and Andy Murray also have matches, while two other U.S. Open winners, Juan Martin del Potro and Lleyton Hewitt, play each other.