Although it was a disappointing result for the new Australian No.1, the Moldovan-born Spaniard put on an impressive performance to beat rising star Joint 6-3 6-1 and reach her maiden WTA 250 final, at the age of 27.
But there was better news for one of Joint's predecessors as Australia No.1 when Kimberly Birrell won the longest match of her career, against Taiwanese Joanna Garland, to reach the final of another WTA 250 event, India's Chennai Open.
Joint has had a stellar year, becoming a WTA champion in Eastbourne, England, in June and reaching the semi-finals of the Korea Open Seoul in September, where she was beaten by Iga Swiatek.
She was favourite to beat the world No.68-ranked Bucsa on Saturday and led 3-2 after five games without a break.
But Bucsa reeled off the next seven games, and though Joint managed to halt that sequence briefly by holding her serve in the fourth game of the second set, the Spanish player took the final three games to wrap up victory in just 58 minutes.
The defeat was a rare setback for the Queenslander, who has soared from outside the top 100 to No.32 in the world and is vying for a seeding spot at the Australian Open in January.
But it was Bucsa's match – she fired down 20 winners while Joint made 25 unforced errors. Bucsa also coughed up zero break point chances.
In the second semi-final, 19-year-old No.3 seed Victoria Mboko won an all-Canadian clash when she defeated No.2 seed Leylah Fernandez, 2-6 6-3 6-2.
In Chennai, Birrell followed up her victory over Croatian third seed Donna Vekic with a monumental performance in a roller-coaster match. Birrell eventually took it 6-7 (2-7) 6-3 7-5 but only after saving four match points.
Garland claimed the first set on a tie-breaker, before Birrell levelled up by winning the second. But the drama was only just starting.
Garland raced into a commanding 5-0 lead but then ran out of steam.
At 5-3, Birrell saved four match points. Then Garland, struggling to breathe, collapsed behind the baseline and took a a medical timeout.
But she was spent and the Australian went on to win in 3hr 19min.
Birrell will face the No.4 seed, Janice Tjen of Indonesia, in the final after she beat Lanlana Tararudee, of Thailand, in two tie-breaker sets.
Also into a final in Chennai is Australia's Storm Hunter, who reached the decider in the women's doubles alongside Monica Niculescu. The No.1 seeds beat Mai Hontama and Akiko Omae of Japan.
Hunter and Niculescu will face Tjen and her compatriot Aldila Sutjiadi, the No.2 seeds, in the final.
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