OSAKA, Japan—Samantha Stosur won the Japan Women's Open for a third time Sunday with a straight-sets triumph against Zarina Diyas in Osaka.

The defending champion Stosur was broken in the first game by the 20-year-old from Kazakhstan, which set the tone for a tight opening set, but the No.1 seed drew on her power and experience to win 7-6 (7), 6-3.

"Zarina played a very good match today," said Stosur, who had to rescue two set points in the tiebreak. "She managed to put me under a lot of pressure and returned serve really well. She gets to a lot of balls and can put you under pressure.

"You have to be out there and try to attack."

Diyas, the No.5 seed, had produced some flashes of brilliance in her first WTA final but couldn't capitalize when seemingly in control and was again unnerved by Stosur's competitive approach when leading 6-5 and 7-6 in the tiebreak.

"Trying to serve out a set in a final, I don't know if maybe she was a little nervous but I tried to play a little bit more aggressive or put a bit more on my shots to make her come up with something else," Stosur said.

The 30-year-old Australian, who didn't drop a set all week, wrapped up the championship with minimal fuss in the second set to collect her first WTA title of the season and sixth career title.

Diyas chose to focus on the positives after a breakthrough week.

"It was my first final so I am happy with how I played," she said. "She served very well, and it was tough, especially on those set points. But this was a great experience for me."