By John O'Brien
SINGAPORE (Reuters) - A calm Sloane Stephens picked her shots to perfection to pull clear for a 7-5 4-6 6-1 victory over Japan's Naomi Osaka in a battle between the last two U.S. Open champions at the WTA Finals on Monday.gi
Both women are making their debuts at the season-ending event, and it was the American who opened Red Group action with a win built on the foundations of solid defense from the baseline and a devastating forehand when she attacked.
"I just competed really well and never gave up," Stephens said in a post-match interview. "I knew I would have to play some really good tennis to beat her, stayed tough and tried to stay as positive as I could and took my opportunities when they presented themselves."
After trading early breaks, the match settled down as the pair enjoyed more success on serve, until Stephens, content to adopt a patient approach from the baseline, broke again in the seventh game when Osaka made a slew of unforced errors.
But Osaka is not one to back down and the 21-year-old Japanese broke straight back to level the contest at 4-4, thanks to some sublime stroke-making aided by a couple of double-faults from her opponent.
After a solid hold from Stephens, Osaka was struggling to contain her emotions as she found the net or went long with her increasingly erratic backhand and the American secured her third break of the match to move a game away from taking the set.
Stephens was growing in confidence as Osaka battled her emotional demons and the American fittingly sealed the opener on her third set point, when the world number four sent another backhand into the net.
Osaka changed her tactics at the start of the second set, finding success by drawing Stephens into the court and away from her baseline comfort zone to hold far more comfortably, but the American used her potent forehand to stay in touch.
Stephens looked the more composed at that stage, but Osaka dug deep and battled back from 15-40 to hold in the fifth game and came out on top of three breaks of serve to send the contest into a decider when the American double-faulted on set point.
The world number six broke immediately at the start of the third set and after Osaka wasted a chance to level things up when she declined to challenge a call that would have been ruled in her favor, Stephens took command of the match.
A pair of easy holds and an another break took her to 5-1, and the 2017 U.S. Open winner sealed the contest on her second match point when an anguished Osaka double-faulted for the fourth time in the match.
"We played a really tough and competitive match so its always an honour to share the court with somebody that good," Stephens added.
Red Group play continues on Monday when Wimbledon champion Angelique Kerber takes on Kiki Bertens of the Netherlands, who was the last player to make it into the eight-woman tournament when world number one Simona Halep withdrew through injury.
(Reporting by John O'Brien; Editing by David Holmes)