Czech tennis players Barbora Krejčíková and číková–SiniakováKateřina Siniaková have formed a successful doubles tennis partnership since 2013. They have won seven major tournaments and nine other Women's Tennis Association (WTA) titles. With wins at the 2020 Olympics and the 2021 WTA Finals, they are the only women's doubles team to complete the career Super Slam together.
Siniaková and Krejčíková are respectively ranked by the WTA No. 1 and No. 2 in doubles .
History
2013–2017: Junior success and early professional years
In 2013, Krejčíková and Siniaková, both aged 17, won three of the year's four junior Grand Slam doubles tournaments. They were paired together when each of them "couldn't find a partner" for doubles at the French Open, and went on to win the event without dropping a set. A month later, they repeated the feat at Wimbledon, and they completed their junior careers with the same result at the US Open. Including two other tournament wins, this stretched their team win–loss record at junior events to 24–0 (48–0 in sets). Siniaková and Krejčíková had peak junior International Tennis Federation (ITF) rankings of No. 2 and No. 3 respectively.
Following their junior triumphs, the team played intermittently from 2014 to 2017. Siniaková was the first to establish herself on the WTA Tour, cracking the top 50 in singles in 2016, while Krejčíková initially struggled, not reaching the top 100 in singles until 2020. This gap in rankings sometimes made it difficult for them to enter the same tournaments, but they did manage to play at several events together in 2016. At the French Open, on the way to their first major women's doubles semifinal, they beat the team of Martina Hingis and Sania Mirza that was attempting to finish a non-calendar-year Grand Slam. They additionally reached the quarterfinals of the US Open.
2018–2020: first Grand Slam titles, Fed Cup win, No. 1 ranking
After a break of more than a year, Krejčíková and Siniaková reunited in 2018. Early that year, they reached their first two WTA Tour doubles finals as a pair in Shenzhen and Miami. In the summer, they reached and won their first Grand Slam finals together: At the French Open, they beat the Japanese pair Eri Hozumi/Makoto Ninomiya in a quick straight-set final, and in the Wimbledon final, they outlasted Nicole Melichar/Květa Peschke . These wins made Krejčíková/Siniaková the first doubles team to complete the Channel Slam since Kim Clijsters/Ai Sugiyama in 2003. The pair nearly replicated their junior triple as the top-seeded team at the US Open, but lost in the semifinals to eventual champions Ashleigh Barty/CoCo Vandeweghe. Krejčíková and Siniaková were the first team in 2019 to qualify for the season-ending WTA Finals, where on their debut in October they finished runners-up to Tímea Babos and Kristina Mladenovic. Shortly before season's end, the team jointly attained the No. 1 ranking for the first time. Additionally, they were named the WTA Doubles Team of the Year.
The next year, Krejčíková and Siniaková qualified for the WTA Finals for a second straight year but did not win any major titles in 2019. They won two tournaments this year, the Rogers Cup in Canada and the Linz Open in Austria. Elise Mertens and Aryna Sabalenka beat them in the Indian Wells final. At the majors, the Czechs lost in the quarterfinals of the Australian Open to eventual champions Samantha Stosur/Zhang Shuai; as defending champions and top seeds, they lost in the first round of the French Open; and they reached the semifinals of Wimbledon, where they lost to Gabriela Dabrowski/Xu Yifan. They fell in round-robin play at the WTA Finals.
In the 2020 season disrupted by the COVID-19 pandemic, Krejčíková and Siniaková reached at least the semifinals of all six events they entered together. Their only title this year came at the Shenzhen Open. In major play, the team's run to the Australian Open semifinals was ended by No. 1 seeds Hsieh Su-wei/Barbora Strýcová, and they lost the French Open semifinal to eventual champions Babos/Mladenovic. The WTA Finals were cancelled this year.