MADRID (AP) — Serena Williams needed just 58 minutes to beat fellow American Sloane Stephens 6-4, 6-0 Monday and reach the third round of the Madrid Open.
The top-ranked Williams broke Stephens four times and saved both break points she faced to secure her 25th straight win. She will next face the winner between former No. 1 Victoria Azarenka and Ajla Tomljanovic.
"She's such a tough player," Williams said of Stephens. "I've never won a 6-0 set against her before, and I don't think I can ever do that again."
Williams remained undefeated in 2015, with her last loss coming in round-robin play at last year's WTA finals.
Earlier, Caroline Wozniacki powered past Christina McHale of the United States 7-5, 6-0 Monday to reach the third round.
The fifth-seeded Wozniacki hit five aces and committed fewer unforced errors on the red clay to beat the 22-year-old player from Teaneck, New Jersey, in 1 hour, 30 minutes. Wozniacki will face Agnieszka Radwanska after the Polish player eased past Casey Dellacqua of Australia 6-2, 6-1.
In the men's competition, John Isner of the United States beat Adrian Mannarino of France 7-6 (2), 6-4 to reach the second round.
The 16th-seeded Isner will next play either Jeremy Chardy - another Frenchman - or Thomaz Bellucci of Brazil.
Also, Steve Johnson of the United States came from a set down to beat Alejandro Gonzalez of Colombia 4-6, 6-3, 7-6 (4).
The 25-year-old Johnson from Redondo Beach, California - one of five Americans in the men's main draw in Madrid - will now have a day to recover before facing third-seeded Rafael Nadal of Spain in the second round.
Sam Querrey beat 19-year-old qualifier Thanasi Kokkinakis of Australia 6-4, 6-7 (6), 6-3, while Feliciano Lopez of Spain overcame Benjamin Becker of Germany 7-5, 3-6, 6-4.
The 11th-seeded Lopez, who lives in Madrid, was given a warning by the chair umpire for using foul language on court during a tense third set.
U.S. Open champion Marin Cilic of Croatia — seeded ninth — beat Jiri Vesely of the Czech Republic 7-5, 6-1 and David Goffin of Belgium rallied to defeat Ernests Gulbis of Latvia 3-6, 6-1, 7-5.
Joao Sousa of Portugal beat Jerzy Janowicz of Poland 6-4, 7-5 and Fabio Fognini of Italy defeated Santiago Giraldo of Colombia 6-2, 6-3.
In the women's tournament, 13th-seeded Lucie Safarova of the Czech Republic bested Tsvetana Pironkova of Bulgaria 6-3, 6-1, Samantha Stosur of Australia beat Kaia Kanepi of Estonia 6-3, 6-2, and 21-year-old Garbine Muguruza of Spain lost to Svetlana Kuznetsova of Russia 6-3, 5-7, 7-5.
Roberta Vinci of Italy beat Alize Cornet of France 6-4, 7-5.
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