Aryna Sabalenka's season ended in disappointment as Elina Svitolina beat the former world number one to claim her place in the knockout stage at the WTA Finals.
Sabalenka took her frustration out on her racquet and reacted to losing a point by crouching to the ground at the back of the court as a semi-final place slipped away.
The Belarusian was able to force a deciding set after unravelling in the latter stages of the first, but lost the final six games in slumping to a 6-3 3-6 6-1 loss.
It came two days after the four-time major winner lost each of the last 11 games as she was thrashed by Mirra Andreeva.
Ukraine's 2018 winner Svitolina will meet Czech world number eight Linda Noskova in the last four after finishing runner-up to Mirra Andreeva, who faces Jessica Pegula for a place in Sunday's showpiece.
Svitolina is appearing at the tournament for the first time since backing up her triumph by reaching the 2019 final, having this season returned to the top 10 for the first time since 2021.
"It was an extremely tough match, especially mentally. I was just trying to play one point at a time," said Svitolina, 32.
"This is the tournament where you bring everything to the table and try to play every game as if it's the last."
This is the first season since 2022 in which Sabalenka has failed to win a major, losing out in the final at both the Australian Open and the US Open.
She claimed three other titles - including completing a rare Sunshine Double with her triumphs at Indian Wells and Miami - and arrived at the Finals with the best win percentage (80.0%, 47-11) on the women's tour this season.
However, that was not enough to maintain her position as the world number one, as she was dethroned after 99 weeks by Elena Rybakina following their US Open title showdown in September.
Unstoppable at her dominant best, Sabalenka has recorded the most straight-set wins by any player this season (43).
She has also won eight of her 13 meetings with fellow top-10 players, with two of those losses coming in major finals against Rybakina, and two arriving this week.
While she has remained consistent on the sport's major stages, reaching at least the semi-finals at 13 of the past 16 slams she has contested, she has lost more major finals (five) than she has won (four) over the past four seasons.
It is in those career-defining moments that she will be desperate to improve - mentally as much as physically - if she is to reassert herself next season.
Sabalenka was bidding for a first success at the season-ending WTA Finals, having made the knockout stages in each of the past four years and lost to Rybakina in last year's showpiece.
But this was another occasion when Sabalenka, unlike Svitolina, appeared unable to maintain a positive outlook in testing moments.
After unravelling against Andreeva, she produced the positive start she desired by firing in an angled forehand winner to clinch an immediate break of serve.
But it was not long before Sabalenka's game again threatened to fall apart as she conceded the first set by losing six of seven games - including twice being broken to love.
The response was excellent, a reduction in unforced errors helping her to a double break and a 5-1 lead before she served out the set at the second attempt.
However, the inconsistency returned and, with it, the frustration. After giving up an early lead in the decider, Sabalenka threw her racquet to the ground as Svitolina remained solid to swiftly turn the set around.
Sabalenka saved two break points, but set Svitolina up to take a third with a double fault, and the world number six kept her cool to serve out victory.
