Serena Williams is playing her eighth Rogers Cup semifinal. On four of those occasions, the former World No.1 has progressed to the final, winning the title three times (in 2001, 2011 and 2013). It is Williams's first last-four showing at a non-Grand Slam tournament since returning from maternity leave in March 2018, and she will face Marie Bouzkova for the first time.
Marie Bouzkova is the fourth qualifier in the last three decades to reach the Rogers Cup semifinals, following Kimberly Po-Messerli in 1996, Yan Zi in 2007 and Kristina Kucova in 2016. It is Bouzkova's first WTA semifinal; previously, the Czech's biggest last-four run was at the Guadalajara 125K in April, where she was runner-up to Veronika Kudermetova. Bouzkova, who cracked the Top 100 three weeks ago with a title at the Nur-Sultan ITF W80 event, had never beaten an opponent ranked higher than World No.74 prior to this week but now has her first two Top 10 scalps of her career after defeating both of last year's finalists, Sloane Stephens and Simona Halep.
Sofia Kenin and Bianca Andreescu will clash for the third time in 2019, the fourth time at pro level and the fifth time overall. The pair have alternated wins over each other to make the head-to-head 2-2 (2-1 in the pros): Kenin won their 2015 Wimbledon girls' first-round encounter 6-3, 6-1 and their Acapulco semifinal this March 6-4, 3-6, 7-5, while Andreescu took their 2017 Rancho Santa Fe ITF W25 semifinal 6-3, 7-6(3) and their Miami second-round tie this March 6-3, 6-3. Kenin and Andreescu were also due to play in the second round of Roland Garros this year - but the Canadian gave Kenin a walkover due to a shoulder injury. In the next round, Kenin would go on to upset Serena Williams to make her debut in the second week of a major.
Bianca Andreescu has won four three-set matches to reach the last four this week, taking her record in three-setters to 15-3 in 2019. The 19-year-old's only losses in the deciding set this year have been to Julia Goerges in Auckland, Anastasija Sevastova at the Australian Open and Sofia Kenin in Acapulco. Andreescu is the first Canadian woman to reach the Rogers Cup semifinals.
Sofia Kenin is seeking to make her fourth final of the season following titles in Hobart and Mallorca and a runner-up finish in Acapulco. It is the American's first semifinal above International level in her career.
ORDER OF PLAY (starts 1pm)
Sofia KENIN (USA) vs Bianca ANDREESCU (CAN)
 Barbora KREJCIKOVA (CZE) / Katerina SINIAKOVA (CZE) vs  Victoria AZARENKA (BLR) / Ashleigh BARTY (AUS)
Not before 6pm
[Q] Marie BOUZKOVA (CZE) vs  Serena WILLIAMS (USA)
 Anna-Lena GROENEFELD (GER) / Demi SCHUURS (NED) vs  Gabriela DABROWSKI (CAN) / XU Yifan (CHN)