|No. 2 seed Radwanska is still looking for her first Grand Slam title. (US Presswire)|
The 19-year-old Stephens won 6-3, 6-4 against the 2010 French Open champion. Stephens has advanced to at least the third round at three of her last four Grand Slam events. She's ranked a career-best 44th.
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At 3-3 in the second set, Stephens broke Schiavone at love, the game ending on a double-fault. The Italian had seven of those in the match - five in her first service game.
Stephens had double match point at 5-3 against Schiavone's serve but couldn't convert. Trying to serve out the match, she fought off a break point then clinched the victory with a forehand winner down the line.
The 32-year-old Schiavone pulled out of New Haven last week because of an illness.
Venus Williams overcame an early deficit for an easy win in her return to the Open. The seven-time Grand Slam champion pulled out of the tournament before her second-round match last year because of an autoimmune disease. Williams returned to beat fellow American Bethanie Mattek-Sands 6-3, 6-1.
Williams, unseeded with a ranking of No. 46, was broken in her first game. But after going down 0-2 in the first set, she won 12 of the last 14 games.
Mattek-Sands is ranked 212th after a series of injuries this year and got in on a wild card.
Keothavong, ranked 81st, had 25 unforced errors to Kerber's nine.
Ranked outside the top 100 at the start of 2010, Kerber is now a career-best sixth. She reached her first Grand Slam semifinal at Flushing Meadows last year.
At age 32, Williams has been learning to deal with the effects of Sjogren's syndrome, which causes exhaustion and joint pain.
In the night session, Serena Williams advanced to the second round, defeating CoCo Vandeweghe 6-1, 6-1 in 55 minutes. Coming off wins at Wimbledon and the London Olympics, Williams looked sharp, committing only nine unforced errors.
In search of her 15th Grand Slam title and fourth U.S. Open championship, Williams improved to 48-1 in first-round matches at Grand Slams. During her on-court interview after the match, she gave a shout-out to another Olympic gold medalist, Carmelo Anthony, who was in the stands cheering for Williams.
Vandeweghe, who fell 7-5, 6-3 to Williams in the Bank of the West Classic final earlier this summer, had trouble dealing with her toss in the blustery wind. She finished with six double faults and only held serve once in seven tries.
Second-seeded Agnieszka Radwanska needed just 54 minutes to advance to the second round of the U.S. Open.
Radwanska beat Nina Bratchikova of Russia 6-1, 6-1 on Tuesday to start play at Arthur Ashe Stadium.
The 91st-ranked Bratchikova had 28 unforced errors to only six for Radwanska.
The Polish star is coming off her first Grand Slam final, a three-set loss to Serena Williams at Wimbledon. She has never made it past the fourth round at Flushing Meadows.
Radwanska retired from her previous match with a sore shoulder while trailing qualifier Olga Govortsova in her opener at New Haven.
Bratchikova was making her U.S. Open debut, but reached the third round at the Australian and French this year.
Ivanovic is coming off a 6-0, 6-0 loss to Roberta Vinci at a tuneup match in Montreal -- not exactly the confidence builder the former French Open champion and top-ranked player was looking for.
"In that first game, I was like, 'Oh my God, at least I should win a game first,' " she said. "It's a lot different. Taking all into consideration, I'm really happy with today's performance."