US Open champion Naomi Osaka said she had “the worst attitude” in her loss to Lesia Tsurenko in the Brisbane International semi-finals.

The Japanese second seed was visibly frustrated as she was beaten 6-2 6-4 by Ukraine’s Tsurenko in just 66 minutes.

Osaka, who won her maiden Grand Slam title in September, said the defeat had taught her “a valuable lesson”.

“I was sulking a little bit, and there are moments that I tried not to do that,” the 21-year-old explained.

“I feel like I didn’t really know how to cope with not playing well.”

The world number five made 26 unforced errors against Tsurenko, and did not create a break opportunity until late in the second set.

Osaka told her coach Sascha Bajin during the match that she did not know why she was “flat”, adding: “I’m putting myself in the situation that either I win the match or I die.”

Speaking after the match, Osaka said: “I feel like, in a way, that this experience for me is better than winning the tournament.

“This helpless feeling I have, I learned sort of what I can do to improve the situation so there aren’t many moments that I feel like that.”

Osaka, who later withdrew from next week’s Sydney International, will move to fourth in the world rankings on Monday.

• GB’s Konta & Watson claim qualifying wins

Teenager Andreescu reaches Auckland final

Canadian teenager Bianca Andreescu continued her remarkable run as she beat Hsieh Su-wei to reach the Auckland International final.

The 18-year-old previously beat Caroline Wozniacki and Venus Williams to set up the meeting with the Taiwanese third seed.

Andreescu saved four break points and hit four aces en route to a 6-3 6-3 victory.

She will face defending champion Julia Gorges on Sunday, after the German beat Slovakia’s Viktoria Kuzmova 6-1 7-6 (8-6).

In Shenzhen, Aryna Sabalenka secured the first WTA title of the year with victory over American Alison Riske.

The Belarusian won 4-6 7-6 (7-2) 6-3 to secure her third career title.