Singapore - Naomi Osaka has set her sights on becoming better on different surfaces, as the US Open champion's season ended in tears at the WTA Finals on Friday.
A left hamstring injury forced the 21-year-old to retire against Kiki Bertens after the Dutchwoman claimed the first set 6-3 in 47 minutes.
It was a bitterly disappointing end for Osaka, who came into the season-finale as the form player but lost three-set matches to Sloane Stephens and Angelique Kerber.
Osaka has had a whirlwind time since her stunning win over Serena Williams in a controversial US Open final.
The triumph cemented her standing on hard court but Osaka has had limited success on clay and grass, where she is yet to make it past the third round at Wimbledon and the French Open.
She struggled on the Singapore Indoor Stadium's hard court, which played slower than expected.
"For me, I shouldn't just be doing well on hard courts. I think I should be doing well on all surfaces," she told reporters. "I think I'm capable of doing that. So definitely I want to try to focus on that next year."
Osaka said she initially injured her hamstring against Stephens in the tournament's opening match.
"There is this level of pain that I can play with, so I definitely was going to play," she said.
"I thought I could finish the match. It just got worse and worse and worse, and then I just couldn't move."
Since winning at Flushing Meadows, Osaka has received overwhelming attention and become a sensation in her homeland of Japan.
"I feel like I have matured," she said. "It's just been a lot of new experiences. I think maybe in the beginning of the year I was very uncertain with what I was doing. But now I feel a bit more calm."
With her season over, Osaka will head home to Florida for the first time in months. "I haven't been home since the US Open," she said.
"I was told I shouldn't really do much. I should just rest for a few weeks."
Results from the WTA Finals tennis in Singapore on Friday (x denotes seeding):
Sloane Stephens (USA x5) bt Angelique Kerber (GER x1) 6-3, 6-3
Kiki Bertens (NED x8) bt Naomi Osaka (JPN x3) 6-3, Osaka retired hurt