Aussie world No.18 Sam Stosur claimed her third Japan Open on Sunday with a straight-sets win against Zarina Diyas in Osaka.

The defending champion hardly had things all her own way though having her serve broken in the opening game and needing to break-back to stay in the first set.

The opener eventually went to a tie-break which Stosur claimed 9-7 having saved two sets points against her 20-year-old opponent from Kazakhstan.

An early break of serve in the second set gave the top seed the ascendency and Stosur eventually powered to a 7-6, 6-3 triumph.

“Zarina played very good match today,” said Stosur after claiming her first title of the season and sixth of her career.

“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.

“It’s great to win a title, and I left it pretty late to try and win one this year, so better late than never!

“But I really love playing this tournament. Three times now – it’s just a great feeling to come back here each year, and if you win the title then it’s even better, obviously!”

Diyas, the No.5 seed showed flashes off brilliance and her undoubted potential competing in her first final but couldn’t capitalise when in front.

“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,” said Stosur.

“Out of the five girls I played this week I’d never played four of them, so quite a few young ones here.

“Zarina’s quite a good player. I’d never seen her play too much before, but I can see why she’s one of the WTA Rising Stars, and I really had to play some good tennis to beat her today.”