Caroline Wozniacki of Denmark returns the ball to Daria Kasatkina of Russia during the Dubai Tennis Championships, in Dubai, United Arab Emirates, Monday, Feb. 20, 2017.
DUBAI, United Arab Emirates — In an all-American matchup, Alison Riske upset 11th-seeded Coco Vandeweghe 6-4, 6-4 to move into the second round at the Dubai Championships on Monday.
The unseeded Riske, making her Dubai debut, has won four of their last five outings.
"I have no idea of that stat, but I'll happily take it," Riske said, smiling. "It's in my favor."
Riske and Vandeweghe, a semifinalist at the Australian Open, were winning teammates on the U.S. Fed Cup team that defeated Germany 4-0 in the first round two weekends ago. They arrived in Dubai straight from Maui on Wednesday.
Vandeweghe seemed to have difficulty getting her firepower going, which is the cornerstone of her game.
In the second set, four of the last five games were service breaks before Riske served out the match at love.
"She was having a little difficulty with her first serves," Riske said. "But she was starting to get back in rhythm in the second set there."
Caroline Wozniacki won her first-round match over Daria Kasatkina of Russia 6-2, 7-5.
The 10th-seeded Wozniacki reached the Doha final last week before losing to Karolina Pliskova.
Wozniacki surrendered her serve twice in the match - in the first game of the first set and the third game of the second set - but otherwise was in control of the court.
"I was really pleased with how I was able to just stay focused out there from the beginning," said Wozniacki, who won the Dubai title in 2011. "It's much different conditions here. The ball is flying. The court is faster than in Doha."
American teen Cici Bellis, playing her first official match of 2017, upset 17th seed Yulia Putintseva of Kazakhstan 6-1, 7-5.
Monica Puig, the Olympic gold medalist from Puerto Rico, needed more than two hours to get past Yaroslava Shvedova of Kazakhstan 6-3, 4-6, 6-4.