Zhuhai - Top seed Daria Kasatkina slammed the tournament scheduling at the WTA Elite Trophy in China on Wednesday after losing in straight sets to Madison Keys.
Kasatkina, 21, was beaten with relative ease by the 23-year-old American, who took 70 minutes to seal the win 6-2, 6-4.
The Russian, who finished her previous round-robin tie against Wang Qiang at 10pm on Tuesday, looked tired on court and had already criticised the match timetable, saying it "sucks".
Asked if she stood by the comments at her post-match press conference on Wednesday, she took a deep breath and said: "Yea. I mean if they want me to pull out of the tournament then they are doing a good job, because in less than 24 hours I've played two matches.
"The girls [Keys and Wang] are not playing tomorrow, they are playing on Friday, and I was supposed to play two matches in less than 24 hours.
"So there's nothing I can say, nothing I can do. I was fighting, I mean I did everything I could.
"I gave more than 100% of my abilities, so this is professional sport."
Keys cruised to take the first set at the Hengqin International Tennis Center, and although Kasatkina put up a fight in the second, the sixth seed clinched the tie.
The American showed little sign of the left knee injury which forced her to retire from her last two tournaments, in Wuhan and Beijing.
After the match, she said: "I think I had a really good start today, and that definitely helped me.
"Overall, I think I just played really solid and went out and did what I needed to do."
Earlier, defending champion Julia Goerges suffered a bruising defeat to Anett Kontaveit.
The fifth seed took a nasty tumble mid-way through the match, which she went on to lose 2-6, 6-4, 4-6 after more than two hours.
Kontaveit, the tournament tenth seed, started brightly, breaking the world no. 14 three times to take the opening set.
Goerges, 29, fell heavily on to the hard court in the sixth game of the second set, and needed to ice her right leg during the changeover.
Clearly slightly rattled, the German nevertheless dug deep to claim the set, pumping her fist and gesturing to her coach as she celebrated.
However, it was the 22-year-old Estonian Kontaveit who won the decider.
The world number 20 Kontaveit has now played both her round-robin matches, after losing on Tuesday to Belgium's Elise Mertens, who will play Goerges on Thursday.
Now in its fourth year the Elite Trophy features 12 players ranked roughly from nine to 20. This year's total prize money is $2.35 million across the singles and doubles tournaments.