World No. 15 Belinda Bencic beat former U.S. Open champion Samantha Stosur in a three-set clash in the second round of the Pan Pacific Open singles competition on Wednesday.
Bencic started the match slowly but managed to turn the tide after losing the first in a tiebreak and facing double break points in the second.
With the match in the balance the 18-year-old Swiss player showed great mental strength against her much more experienced opponent, winning eight of nine games from 2-2 in the second to win the second 6-3 and go up 4-0 in the final set. She then went on to close out the third 6-4.
"Sam was serving great today, so I had a lot of trouble when I was returning. And the third set was difficult too — I had 4-0, then it was 4-3 — so it got a bit tighter," she said on court after the match.
"I'm happy I could just stay calm and serve it out in the end. I'm very happy with this win."
World No. 8 Garbine Muguruza had little trouble beating Czech Barbora Strycova in straight sets 6-3, 6-4 to set-up a quarterfinal meeting with Bencic.
Like Bencic, World No. 9 Angelique Kerber survived an early scare to overcome United States' Madison Brengle 5-7, 6-1, 6-0.
Denmark's world No. 6 Caroline Wozniacki was too good for Croatia's Ana Konjuh, winning 6-2, 6-2.
In the doubles competition earlier on Wednesday, Japan's Misa Eguchi and Junri Namigata had a walk-over victory against Bencic and Kristina Mladenovic.