(REUTERS) - Madison Keys beat former No. 1 Caroline Wozniacki for the first time on Sunday (April 7), overpowering her 7-6 (7-5), 6-3 to win the Charleston Open in South Carolina.
The title, her first on clay court, broke a nearly two-year drought for the eighth-seeded American, who claimed her fourth career success.
In Mexico, Spain's Garbine Muguruza successfully defended her Monterrey Open title when Victoria Azarenka retired injured from her first WTA singles final in three years.
Second seed Muguruza was leading the match between the two former world No. 1s 6-1, 3-1 when Azarenka decided she was unable to continue because of an injury to her right leg.
"It's unfortunate I couldn't give my best today, but I tried my hardest," a tearful Azarenka, who had not previously reached final since the birth of her first child in December 2016, said at the presentation.
"I want to say thank you to my son Leo, who is not with me here. I would love him to be here to share this with me because it is special."
The crowd responded with a chant of "Vika! Vika! Vika!".
Muguruza's victory never looked in doubt and ensured that the record run of different women winning WTA titles this season would be extended to 16 tournaments.
"It's a great feeling to come back and defend a title," she said in a courtside interview. "It's never easy."
Azarenka received treatment on her leg during a medical time-out between sets, but it became apparent as the second set began that her movement had become significantly hampered.
Keys' previous two losses to Wozniacki had been on hard courts when she failed to win a set.
"I think I served really well today, said the 24-year-old, who had predicted on Saturday that playing on clay would be beneficial in her bid to defeat the Dane.
"I also felt I kept a lot of pressure on her, making a lot of returns and keeping rallies going and not going for things too early," said the world No. 18, who won 76 per cent of points on her first serve, and fired six aces.
"More than anything I really trusted my game and went for my shots."
That was most evident late in the first set and the tiebreak. The big-serving Keys trailed 5-6 in the opening set before forcing the tiebreak, which remained close until 4-3 when the fifth-seeded Wozniacki double faulted.
Keys won the next point but twice had backhand errors to allow Wozniacki to pull within 6-5. A backhand down the line enabled Keys to finally claim the set.
"I just knew the games I was losing in the first set I was just being too tentative and not really trusting my shot," said the 24-year-old American. "I knew I had to go for it. I think that's how I have to play... 100 per cent believing in my game."
Keys broke Wozniacki in the sixth game of the second set to go up 4-2 and when she made it 5-2 that all but clinched the match.
"It's definitely been a really great week for me, especially after having some really tough losses the last couple of weeks," Keys said. "It definitely is a very good springboard for heading over to Europe."