CNN  — 

An eventful season for Naomi Osaka came to an unfortunate end Tuesday when the Japanese megastar pulled out of the WTA Finals in Shenzhen, China with a right shoulder injury.

Osaka withdrew hours before her second match at the year-end championships against fellow grand slam winner Ashleigh Barty and will be replaced by alternate Kiki Bertens of the Netherlands. Osaka had defeated Petra Kvitova in three sets on Sunday in a rematch of January’s similarly gripping Australian Open final.

“I’m disappointed to have to withdraw from the Finals,” Osaka said in a statement released by the WTA. “It has been a great event in Shenzhen, and it’s the biggest WTA event of the year. This is not how I wanted to end this tournament or my season. I look forward to getting healthy and hope to be back here in Shenzhen next year.”

SINGAPORE - OCTOBER 28:  Elina Svitolina of the Ukraine poses with the Billie Jean King trophy after her win against Sloane Stephens of the United States during the Women's singles final match on Day 8 of the BNP Paribas WTA Finals Singapore presented by SC Global at Singapore Sports Hub on October 28, 2018 in Singapore.  (Photo by Yong Teck Lim/Getty Images for the WTA)
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Osaka’s clash with world No. 1 Barty was all set to be a blockbuster. They met earlier in October in the final of a big tournament in Beijing and it didn’t disappoint with Osaka rallying for a three-set victory.

Osaka, though, said she injured the shoulder there. And in Japan in the buildup to the WTA Finals, she barely hit a serve.

“I didn’t serve for a while when I was in Japan,” the 22-year-old was quoted as saying by the WTA. “I just started serving the last two days. Felt better, came here, then I played my match.

“I felt it immediately. When I woke up the day after, it was throbbing and stuff. Didn’t serve at all yesterday.”

She suspected the injury wasn’t overly serious.

Past injury

“I injured my shoulder like five years ago or something but not heavy,” Osaka said. “It was in Thailand when I was like 17 or something. It wasn’t that big of a deal. I just had to rest it. I’m hoping it’s more like that.

“It doesn’t feel like it’s anything more serious than muscular. I think if it was bone-related then I wouldn’t be able to lift it, but I am able to do that. It’s just a little bit painful.

“Definitely I don’t think it’s something that I would immediately need surgery for. I’ve never gotten surgery, so I feel like I’m very lucky on that.”

NEW YORK, NY - SEPTEMBER 08:  Naomi Osaka of Japan poses with the championship trophy after winning the Women's Singles finals match against Serena Williams of the United States on Day Thirteen of the 2018 US Open at the USTA Billie Jean King National Tennis Center on September 8, 2018 in the Flushing neighborhood of the Queens borough of New York City.  (Photo by Julian Finney/Getty Images)
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The silver lining is that Osaka ends her campaign by winning 11 straight matches. She began the streak by clinching a title in her birthplace of Osaka, Japan in September.

But it hasn’t all been smooth for the baseliner with the often devastating power game.

The shoulder issue was the latest injury to affect Osaka this season, having suffered from minor abdominal and hand complaints during the clay-court swing and a knee injury on the eve of the US Open – where she was the defending champion.

On the court, Osaka sizzled in Melbourne to land a second straight grand slam title and rose to No. 1 in the rankings. But she split from influential coach Sascha Bajin and admitted to struggling with heightened expectations.

Away from the hard courts, clay and grass proved to be sterner tests. Escaping in her first two matches at the French Open, Osaka fell in the third round before a first-round exit at Wimbledon. She also admitted that tennis for a time just wasn’t fun anymore.

Naomi Osaka pulled out of the WTA Finals due to injury Tuesday. But before then, she won a title at home in Japan last month.

Osaka was upset by Belinda Bencic in the fourth round at the US Open, 12 months after downing Serena Williams in a controversial final in Flushing Meadows.

She produced the perfect response in Asia, only to now be derailed by the shoulder injury.

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In Tuesday’s other Red Group tussle, Kvitova faces Bencic. Both hold 0-1 records following defeats to Osaka and Barty, respectively.