Naomi Osaka, Petra Kvitova, Madison Keys into Brisbane International semifinals

Brisbane International, Brisbane International Semi Final, Australian Open defending champion, Naomi Osaka, two-time Wimbledon winner, Petra Kvitova, Madison Keys, Madison Keys Fourth Attempt, Brisbane defending Champion, Karolina Pliskova, Karolina Pliskova vs Alison Riske

Osaka beat Kiki Bertens 6-3, 3-6, 6-3 ( AP Photo)

Defending Australian Open champion Naomi Osaka, two-time Wimbledon champion Petra Kvitova and Madison Keys won quarterfinal matches Friday at the Brisbane International.

Osaka beat Kiki Bertens 6-3, 3-6, 6-3, Kvitova defeated qualifier Jennifer Brady 6-4, 6-2 and Keys beat fellow American Danielle Collins 6-4, 6-1. Brady was coming off wins over Maria Sharapova in the first round and top-ranked Ash Barty in the second.

Keys, a 2017 U.S. Open finalist, reached the semifinals in Brisbane for the first time in four attempts.``Happy to get a lot of matches in and feel like a lot of what I was working on during off-season is kind of immediately clicking,`` Keys said.

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``There are still some things that I want to do a little bit better, but it's definitely a great starting point for the year.``

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In a later quarterfinal, Brisbane defending champion Karolina Pliskova played Alison Riske.