Canada's Gabriela Dabrowski and New Zealand's Erin Routliffe remain undefeated in women's doubles at the WTA Finals in Riyadh, Saudi Arabia.

The 2023 U.S. Open champions, seeded second at the event, secured a 1-6, 7-6 (1), (11-9) super-tiebreak win over fourth-seeded Italians Sara Errani and Jasmine Paolini in round-robin play on Tuesday.

The season-ending tournament features the WTA Tour's top eight women's doubles teams.

Dabrowski and Routliffe lost the first set in 22 minutes but levelled the match by breaking Errani's serve three times in the second, including at 6-5. They clinched victory with Routliffe saving a match point on her serve and Dabrowski ending Errani's final serve-and-volley attempt.

"What happened on match point? Big serve? Sounds about right," Dabrowski said of Routliffe's match-saving serve.

"It was such a challenge to try to raise our level," she added. "To try to play against a team that plays a little bit differently than others, with Errani serve-and-volleying and stuff like that. It's kind of things that we do, but don't necessarily play against a lot. Pretty proud of us for the adjustments we made."

Dabroswki and Routliffe improved to 2-0 after cruising to a straight-sets win over Chan Hao-Ching and Veronika Kudermetova.

"That was a really, really fighting match," Routliffe said of Tuesday's match. "I'm glad we put on a show for you guys, but I hope the next match won't be as exciting."

Dabrowski and Routliffe will next face fifth-seeded Americans Caroline Dolehide and Desirae Krawczyk on Thursday, where a win would secure a spot in the semifinals.

The final is scheduled for Saturday.

Coco Gauff earned her second career win over Iga Swiatek, winning 6-3, 6-4 to reach the semifinals.

It was Gauff's first victory over Swiatek since the 2023 Cincinnati Open. The result snapped Swiatek's six-match win streak at the finals.

The win moved Gauff to 2-0 in the Orange Group, while Swiatek fell to 1-1. Swiatek had rallied to beat Barbora Krejcikova in three sets on Sunday in her first match in two months.

Krejcikova, the Wimbledon champion, kept her chances of advancing alive with a 6-3, 6-3 win over Jessica Pegula.

The result eliminated Pegula, who lost in straight sets to Gauff in their opening match in Saudi Arabia.

Aryna Sabalenka of Belarus clinched her first-ever, season-ending world No. 1 ranking by virtue of Gauff's victory Tuesday.

Swiatek held the No. 1 spot most of the season until Sabalenka overtook her on rankings points on Oct. 21. Sabalenka bookended her season with Grand Slam wins at the Australian Open and U.S. Open.

Only Swiatek could have overtaken Sabalenka for the top spot, but the Swiatek loss gave Sabalenka a lead of 1,246 points with only 1,100 points left to earn.

She told reporters in Riyadh that the news surprised her.

"I was like, 'How? What happened?' My boyfriend actually told me, like, 'Oh, congrats, you became world No. 1.' I'm like, 'What?'"

Sabalenka, 26, entered the WTA Tour Finals last season at No. 1, but Swiatek didn't drop a match and regained the top ranking.

Novak Djokovic won't defend his ATP Finals title after ruling himself out Tuesday citing an injury, leaving the season-ending event without a member of the Big Three of men's tennis for the first time in 23 years.

"I was really looking forward to being there, but due to ongoing injury I won't be playing next week," Djokovic wrote on social media, without specifying what the problem is. "Apologies to those who were planning to see me."

The eight-man tournament begins Sunday in Turin, Italy.

Djokovic has won the ATP Finals a record seven times. He beat current No. 1 Jannik Sinner for the title last year.

Roger Federer, who announced his retirement in 2022, won the event six times after making his debut in 2002; Rafael Nadal, who is retiring after playing in the Davis Cup this month, was the runner-up twice at the ATP Finals but never won it.

Not since 2001 has the tournament been held without at least one of Djokovic, Federer or Nadal. This season also was the first since 2002 without at least one Grand Slam title for a member of that trio.

Djokovic finishes the year with a 37-9 record but only one tournament championship: his first Olympic gold medal, which came at the Paris Games in August. That was his 99th tour-level title.

Djokovic did not add to his men's-record 24 Grand Slam trophies in 2024 and dealt with a torn meniscus in his right knee that required surgery and forced him to withdraw from the French Open before the quarterfinals. After bowing out of the U.S. Open in the third round, he played one Davis Cup match and then reached the final of the Shanghai Masters last month, losing to Sinner. He withdrew from the Paris Masters.

Besides Sinner, the other ATP Finals qualifiers were Carlos Alcaraz, Alexander Zverev, Daniil Medvedev, Taylor Fritz, Casper Ruud, Alex de Minaur and Andrey Rublev.

With the finals of the Billie Jean King Cup and Davis Cup set to be played in Malaga, Spain, this month, the International Tennis Federation is making a donation to the Spanish Red Cross to support relief and recovery efforts for the recent catastrophic flooding in the country.

The ITF and its two team tournaments said in a news release Tuesday that they "express their deepest sympathy to the victims and support for the communities and families affected by the devastating floods in Spain and its regions."

The Billie Jean King Cup and Davis Cup, along with the ITF, "are donating to the Cruz Roja, and we encourage all our fans and followers to contribute as well."

The ITF did not say how much it is donating.

Authorities have recovered more than 200 bodies in the eastern Valencia region after heavy downpours caused flash flooding. Police, firefighters and soldiers continued to search Tuesday for an unknown number of missing people.

The Billie Jean King Cup matches are scheduled for Nov. 13-20, and the Davis Cup -- the last event of 22-time Grand Slam champion Rafael Nadal's career -- is set for Nov. 19-24, all in Malaga.