Iga Swiatek was remarkably dumped out of the WTA Tour Finals despite demolishing Daria Kasatkina in only 51 minutes on Thursday. Coco Gauff's defeat against Barbora Krejcikova means that the world No 2 is heading home from the tournament in Saudi Arabia.

Swiatek thrashed Kasatkina 6-1 6-0 in under an hour but the tight nature of the group meant that she needed Gauff to see off Krejcikova. The American star stuttered and struggled with her serve, falling to a 5-7 6-4 loss.

Krejcikova's victory meant that she finished top of their group with Gauff in second. Only the top two players were able to advance to the semi-finals, meaning Swiatek was dumped out.

A Gauff victory was the only way Swiatek would have advanced due to a complicated tiebreaker in the tournament's rules. Krejcikova only needed two sets to see off Gauff, but would have finished second and her opponent top even if she completed a victory in three sets.

Swiatek revealed that she was unaware that she needed Gauff to defeat Krejcikova and seemed confused when the rules were put to her. “Um, you mean [the win over Kasatkina] didn’t matter? What?” she responded in her press conference.

Jessica Pegula pulled out of the tournament ahead of her scheduled match against Swiatek. It meant that the 23-year-old’s result against Kasatkina - Pegula’s replacement - was not included in the semi-final calculations.

When that was explained to her, the Pole paused and joked: “Huh?”

Asked if it was good that she was unaware of the stipulation, she added: “Honestly, I don’t think it matters. Like we go out on court to win every match anyway, so I was not thinking about that. I did not know that was the case.

“You know. I’m professional enough to always give 100 percent no matter what the stakes are. So, no.”

Wimbledon champion Krejcikova will play in the semi-final as the lowest-ranked player in the tournament. She has rekindled her form in Riyadh and reflected after beating Gauff: “It’s tough to say. As you said it was very up and down.

“The Wimbledon victory is definitely the highest point of my career so far. Being here and being able to qualify for the finals, reaching the semis is something unimaginable before this tournament. I’m really proud of myself. I’m looking forward to the new challenges.”