TORONTO, Canada - No.1 Ashleigh Barty's opening round loss to Sofia Kenin at the Rogers Cup has opened the door for former No.1s Naomi Osaka and Karolina Pliskova to leave Canada with the top spot. 

With last year's Montreal points dropping off, Barty came into the Rogers Cup with a slim 27 point lead on No.2 Osaka, and a 205 point lead on No.3 Pliskova. Barty's opening loss means Osaka is a win away from guaranteeing the No.1 ranking switches hands after Canada. 

Here are the scenarios:

- If Naomi Osaka defeats Tatjana Maria in her opening match on Wednesday, there will be a new No.1 on Monday.

- Karolina Pliskova must advance to the semifinals to have a chance at returning to No.1, however, if Osaka advances to the quarterfinals, then Pliskova would need to reach the final. 

- In the event they meet in the championship match, the winner would take home the title and No.1 ranking.

- If Osaka loses her opener and Pliskova does not reach the semifinals, then Barty will remain at No.1.

Since ascending to No.1 after winning her third title of the season in Birmingham, Barty has held the No.1 ranking for 8 weeks. The 23-year-old Australian took over the top spot from Osaka, who had held the No.1 since winning her second major at the Australian Open in January, a total of 18 consecutive weeks. 

Pliskova is looking to return to No.1 for the first time since 2017, when she became the first woman representing the Czech Republic to hold the top spot. Pliskova will open her Toronto campaign against Alison Riske.