Reigning US Open champion Sloane Stephens opened her Washington Open campaign by beating fellow American Bethanie Mattek-Sands 7-5, 6-4.
Third-ranked Stephens, who captured her first Grand Slam title last year in New York, rallied from 5-2 down in the first set to book a second-round match against Germany’s Andrea Petkovic.
“I’m super excited about the hardcourt season again,” Stephens said. “It was good I was able to fight back and win.”
Stephens, who won her first WTA title at Washington in 2015, fired her sixth ace on her first match-point chance to advance after one hour and 53 minutes.
“I knew I was in for a real test from the very beginning,” Stephens said. “I knew I had to be patient, play my game and wait for my opportunities.”
Stephens became the top-rated player in the draw when world number two Caroline Wozniacki, the reigning Australian Open champion, withdrew due to a right leg injury.
Stephens’ top-rated remaining rival is Japan’s 17th-ranked Naomi Osaka, the reigning Indian Wells champion who won her Washington debut 6-2, 7-6 (7/4) over American Bernarda Pera.
“Confidence-wise, winning Indian Wells was good for me,” Osaka said. “It has helped me a lot.”
Top seed Wozniacki said after practice Monday she had a right leg issue. The 28-year-old Dane won her 29th career WTA title in June at Eastbourne but was ousted from Wimbledon in the second round.
“It’s just something that has been nagging for a little while,” Wozniacki said. “Hopefully it will be fine.”
Wozniacki captured her first Grand Slam title at Melbourne in January, returning to world number one after a six-year gap, the longest span between reigns in women’s tennis history.
Wozniacki withdrew hours before her scheduled opening match against Ukraine qualifier Anhelina Kalinina. She will be replaced in the draw by qualifying lucky loser Ysaline Bonaventure of Belgium.
Naomi Osaka (JPN x3) bt Bernarda Pera (USA) 6-2, 7-6 (7/4)
Ana Bogdan (ROM) bt Ekaterina Makarova (RUS x4) 7-6 (7/2), 6-3
Nao Hibino (JPN) bt Sofya Zhuk (RUS) 7-5, 6-4
Donna Vekic (CRO x7) bt Caroline Dolehide (USA) 6-3, 6-4
Belinda Bencic (SUI x6) bt Harriet Dart (GBR) 7-5, 6-2
Sloane Stephens (USA x2) bt Bethanie Mattek-Sands (USA) 7-5, 6-4
Yulia Putintseva (KAZ x8) bt Tatjana Maria (GER) 6-3, 3-6, 6-4