Re: Tight battle in 3 for WTA World #1 @ Rogers Cup (Toronto). Chart with scenarios
So basically to keep her number 1 spot Barty has to make it at least as far as Osaka. Now as far as Pliskova goes, that's a bit more complicated but also tougher on Karolina. She needs to at least make the semifinals, which won't be easy in that draw, and that's assuming Barty loses early, which is highly unlikely (she made semifinals here last year, losing to eventual champion Halep).
Yeah, I too think she is safe until the USO (Halep is defending way too many points between Canada and Cincinnati, Osaka is concentrating on her USO defense and Pliskova is dangerous, but also quite fragile under the pressure of playing to get to number 1). After that, who knows, if it's anyone of the top 3 in the Race winning (her, Pliskova, Halep) then that will most certainly be it and probably also it for the Race and YE based on how things have gone in the past.