The Chinese player, seeded 27th and headed for the fourth round of the Australian Open, has spent months building up her strength — and confidence.

Credit...Asanka Brendon Ratnayake for The New York Times

MELBOURNE, Australia — Wang Qiang says she lost so quickly to Serena Williams in the United States Open quarterfinals last year that it hardly left a mark: 6-1, 6-0, 44 minutes.

“A really tough match, you’ll always remember,” Wang said in an interview with The New York Times on Friday. “That one was easy — I think I didn’t play two balls in a row, so for me it’s easy to forget it.”

She will always remember the rematch, however: The 27th-seeded Wang beat eighth-seeded Williams 6-4, 6-7(2), 7-5 on Friday in the third round of the Australian Open, hanging tough for two hours and 41 minutes with the 23-time Grand Slam champion who had overwhelmed her five months earlier.

“To be honest, I didn’t think I can win this match,” Wang admitted. “Because last time it was love-and-one, and who knows what tennis I will play?”

Wang, 28, had struggled to believe that she belonged in the top echelon of the sport she has played professionally for roughly a dozen years, even after reaching a career-high ranking of No. 12 last year.

“When she was talking about the girls two spots in front of her, she was talking like they were not from the same world,” said Thomas Drouet, Wang’s coach. “I’m sure she believes now, ‘Yes, I am one of them.’”

Wang’s sights are now set on the ultimate prizes in tennis. She dreams of becoming the second Chinese woman to win a Grand Slam title, following Li Na, who won the 2011 French Open and the 2014 Australian Open.

Li’s trailblazing led the WTA to invest heavily in expanding the tour throughout China, which has allowed Wang to aim for big goals close to home. Wang is based in Shenzhen, site of the WTA year-end championships for the tour’s top eight for the next nine years, which awards over $4 million to the champion.

“Every player, they want to be top 10 and play finals — and it’s really big money,” she said.

Nicknamed “Q,” Wang already earns plenty in endorsements in China, where she has been known more for her bubbly personality and photogenic appearance than for her prowess on the court. She has speculated that officials with China’s tennis federation were first drawn to her because she was pretty, then realized she was actually pretty good at tennis, too.

She was plenty good on Friday against Williams. Drouet said the key was Wang’s ability to forget what had happened just months before in New York. “There she put a lot of pressure on playing Serena, on playing on Arthur Ashe for the first time,” Drouet said. “So, mentally, we tried to work on that aspect of the match. She has to stay herself. She has to stay Q, with her personality and her style of game, and play like any other match.”

Staying true to her style of game meant being aggressive, which she had been unable to do in New York, hitting zero winners. On Friday afternoon in Rod Laver Arena, bolstered by increased strength, she hit 25 winners. That prevented Williams from easily overpowering her.

“We worked really hard in the off-season,” Wang said. “We did a lot in the gym, so I have more power now. I have confidence, so much more confidence than last year.”

Drouet, who now also directs her physical training, said he emphasized adding upper body strength after seeing her get knocked around by Williams in New York. “I said, ‘You see, to challenge these girls you need more power,’” Drouet said.

And while Drouet believes steadiness will always be the foundation of Wang’s game, he has pressed her to be less passive compared with last season.

“She couldn’t win big tournaments waiting for the other one to miss,” Drouet said. “She’s almost doubled her winners per match.”

Wang’s reward for beating Williams is being the clear favorite in her fourth-round match Sunday against 78th-ranked Ons Jabeur of Tunisia, against whom she is 2-0.

Wang first surged up the WTA rankings in the second half of the 2018 season, rising from 91st to 20th primarily on the strength of her performances at tournaments in China and Hong Kong, where she went 23-5.

She has worked to convince herself that her home-court advantage can travel. “If you can beat someone in China, why can’t you beat them in other countries?” Wang said. “And here we’re very near to Chinatown, so I have the Chinese food — that’s the way.”

She reached a career high of 12th in the rankings after her run in New York last year, which included a win over second-seeded Ashleigh Barty. The win was emotional for Wang. It came soon after the death of her former coach Peter McNamara, an Australian doubles champion who passed away from prostate cancer in July.

“I always dream about him,” Wang said Friday of McNamara. “I think he can see what I played today. He will be proud of me.”