Monica Puig comes back from the brink to oust Petra Kvitova in Pan Pacific Open.

Monica Puig battled back from 4-2 down in the final set to stun Petra Kvitova and reach the quarter-finals of the Pan Pacific Open.

The Olympic singles champion from Puerto Rico also overcame a dreadful start to post a 1-6 6-4 6-4 victory in two hours and 10 minutes.

After losing the first five games of the contest, the 22-year-old discovered her range but still teetered on the edge during a tight second set.

She saved one break point in game three before recovering from 15-40 down on serve in the seventh.

In all, she saved five break points in the second - including one more at 4-4 - before pouncing to register the only break of the set in game 10, which enabled her to take the match into a decider.

Up until this point, it was the two-time Wimbledon champion from the Czech Republic who had controlled matters in Tokyo.

Kvitova, the world No 16 and seventh seed, conceded just eight points from her opening eight service games and appeared in total control.

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She made the first break of serve in the decider but, from 4-3 and 40-15 up on serve, the 26-year-old's game began to unravel and she ended up losing 10 of the last 11 points of the match.

Puig, the world No 33, said: "It was difficult conditions today. The conditions were heavy and the roof was open this time so it took me a little bit of time to adjust."

Puig has yet to lose to a left-hander during 2016 and her next opponent will be either defending champion Agnieszka Radwanska or Barbora Strycova.