The young Australian, who pulled out all the stops in the previous round to eliminate China's Lin Zhu 7-5 7-6 (12-10), went down 6-3 6-1 to Katerina Siniakova on Wednesday.
Even though the Czech was marginally down on her first-serve percentage compared to the teenager (62-59 per cent), Siniakova won a healthy 70 per cent of points on her first serve to Joint's 45 per cent.
Siniakova will now meet American Iva Jovic for a place in the quarter-finals.
Jessica Pegula, who was twice broken while serving for the match in the third set, recovered to edge Hailey Baptiste in a tight tiebreaker to go through.
Sixth-seeded Pegula beat her fellow American 6-4 4-6 7-6 (8-6) on her seventh match point to reach the third round.
Pegula, who lost in the China Open semi-finals last week, will next play ninth-seeded Ekaterina Alexandrova, who beat American Ann Li 7-6 (7-5) 6-2.
No.3 seed Coco Gauff easily defeated Japan's Moyuka Uchijima, while top-ranked Aryna Sabalenka overcame an early scare to beat unseeded Rebecca Sramkova 4-6 6-3 6-1.
US Open champion Sabalenka broke her 68th-ranked opponent in the opening game of the final set and went on before converting her second match point to win in almost two hours.
"I knew that after that little break … it will be not that easy to get back in my rhythm," Sabalenka said in her on-court interview. "I'm really glad that in the second set I found my game and stepped in and I think I played really great."
She faces next No.16 seed Liudmila Samsonova who rallied to beat 2020 Australian Open champion Sofia Kenin 3-6 6-3 6-1.
Sabalenka, who took a Greek holiday after her second consecutive win at Flushing Meadows, withdrew from last week's China Open - another WTA 1000-event.
"I feel good," Sabalenka said on her arrival in Wuhan. "I just didn't want to rush my body into the tournament. So I think we made the right decision to take extra time for recovery and for the preparation. Physically, I feel ready to go."
Sabalenka has had an amazing run in Wuhan - her record is 17-0 while winning titles in 2018, 2019 and 2024.
No 11 seed Naomi Osaka was beaten in straight sets by Linda Noskova.
After a hard-fought opening set, the Czech won 7-6 (7-2) 6-3 to advance to the last 16.
On Tuesday, No.4 Amanda Anisimova, the runner-up at both the US Open and Wimbledon this year, withdrew from the Wuhan tournament citing a left calf muscle injury after winning the China Open title.
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