BRISBANE (AFP) - Reigning US Open champion Naomi Osaka said her poor attitude was costly during her 6-2, 6-4 loss to Lesia Tsurenko in Saturday's (Jan 5) Brisbane International semi-finals.
The 21-year-old second seed went into the match as firm favourite but looked flat from the outset, as the Ukrainian world No. 27 raced through the match in just 65 minutes.
The Japanese tennis star, who burst to prominence with her eventful US Open final win over Serena Williams, made 26 unforced errors and was broken three times in a disappointing display.
She said after the match that she did not know how to cope once things started to go against her.
"If I'm being really frank, I just feel like I had the worst attitude today," she said.
"I feel like I didn't really know how to cope with not playing well.
"I was sulking a little bit, and like there are moments that I tried not to do that, but then the ball wouldn't go in, and then I would go back to being, like, childish and stuff.
"I feel like last year I did a lot of that," she added.
"I'm trying to change it more, and I think I have."
Her compatriot Kei Nishikori, meanwhile, was in superb form as he demolished Jeremy Chardy 6-2, 6-2 in the men's semi-finals of the tournament.
The 29-year-old second seed gave his French opponent no chance as he put on a commanding all-court display to advance to the final for the second time in three years.
After his impressive straight sets quarter-final win over Grigor Dimitrov, Nishikori said he had set his sights on returning to the world's top five after falling to No. 39 last April due to a wrist injury at the end of 2017 that required time away from the tour.
And he showed all the qualities of a top-five player in his 66-minute demolition at the Pat Rafter Arena.
Nishikori served only two aces compared with the 11 sent down by Chardy, but he returned superbly and pressured the Frenchman's serve throughout, breaking him twice in each set.
He also moved around the court well, his speed not noticeably affected by the injuries that hampered him last year. "Everything was working well today," he said.
"I felt like I was too fast on the court today - I felt very good. "Physically and tennis-wise I think it was perfect. I served well, I returned well - I think that was the key today - and I was moving well, that was fantastic."
Nishikori was runner-up to Dimitrov in 2017 and will go into Sunday's final as firm favourite against fourth-seeded Russian Daniil Medvedev, who beat Frenchman Jo-Wilfried Tsonga 7-6 (8-6), 6-2.
Osaka said Saturday's loss was probably a better learning experience than if she had made the final.
"I think today I learnt... what I can do to improve the situation," she said.
The 29-year-old Tsurenko, who will now rise to a career-high world ranking of 24th, said she had adopted a new game plan during the off-season.
"I feel better with my serve and that I am moving well," she said.
"I feel more strong now, so I can kind of handle every kind of pressure on court, even when someone like Naomi is playing really strong.
"I can really stay there and I can be aggressive also."
In the final, Tsurenko will play fifth-seeded Czech Karolina Pliskova, who beat Croatia's Donna Vekic 6-3, 6-4.