Heather just isn't hitting through the ball, on a treacly Montreal court, and is making too many simple unforced errors on standard rally shots. Her groundies don't look grooved like they did when she first appeared on tour.
She had BP on both opening Stosur service games, couldn't take them, and then in a long second service game of her own, she was broken. An UE. I think she must be at a dozen already at least. It's not the same Heather that she was 4 years ago, the game has changed, but not improved - other than the first serve when it goes in.
Also don't think it's a great matchup for Hev, with her lack of height finding it tough to return the vicious top spin/kick shots which come off Stosur's racket.
CD will be happy to see that her favourite British coach is in Hev's box this week ;)