BRISBANE, Australia (AP) -- Naomi Osaka responded to some courtside advice from her coach in the most emphatic way after dropping the first set in the Brisbane International quarterfinals, conceding only five points in the next set on her way to a 3-6, 6-0, 6-4 win over eighth-seeded Anastasija Sevastova.
The U.S. Open champion was clearly under pressure in the first set Thursday, when she made 15 unforced errors and had fewer winners than Sevatsova, who had won both of their head-to-head meetings last year and had already converted two service breaks.
A disconsolate-looking Osaka went to a courtside chair at the changeover. And whatever coach Sascha Bajin, a former hitting partner for Serena Williams, told her during a quick, animated conference worked.
She finished with 11 aces, converted all four of her break-point chances in the second and third sets and appeared far more confident in her own game.
Osaka said the advice was merely a reality check.
"I mean, I was just trying to stay calm. Was trying to tell myself, 'She's one of the best players in the world. I just have to stay in there, and hopefully I'll get a chance,'" Osaka said. "I did, so I just kept trying to roll with it. He literally told me that."
The 21-year-old Osaka will play either Lesia Tsurenko or Anett Kontaveit in the semifinals, and now could rise to No. 3 in the rankings next week -- which would be a high for a player from Japan.
Osaka has now made the semifinals or better at four of her last five tournaments, a streak that began with her run to a first major title that culminated with a memorable win over Williams in the U.S. Open final. And it has all been a significant boost to her confidence ahead of the Australian Open, which starts on Jan. 14.
"I feel like right now I'm really confident in myself, and I feel like the offseason training that I've been doing is really paying off," she said. "And I'm not sure if I would have had the same feeling six months ago. Six months ago I didn't win the U.S. Open."
Jeremy Chardy beat Japanese qualifier Yasutaka Uchiyama 6-4, 3-6, 7-6 (4) to be first through to the semifinals, where he will meet either second-seeded Kei Nishikori or 2017 champion Grigor Dimitrov, who play later Thursday.
Jo-Wilfried Tsonga got an easier path to the quarterfinals than expected, avoiding a second-round contest with 17-time Grand Slam champion Rafael Nadal, who withdrew from the tournament with a thigh muscle strain on Wednesday.
Tsonga beat Taro Daniel 7-6 (5), 6-3. The 77th-ranked Daniel was the lucky loser from qualifying who got a spot in the main draw when Nadal pulled out.
"You go from the challenger to the guy that is supposed to win -- it's not easy," Tsonga, a 2008 Australian Open finalist, said of the difference.
It was the first time in almost a year that Tsonga recorded back-to-back wins at the elite level after spending most of 2018 out following knee surgery in April.