Graf sent Kerber, her fellow countrywoman, a text message congratulating her on reaching her first Grand Slam final.
In Melbourne, she handed Angelique Kerber her first slam - and the German immediately went on a losing streak, before arriving here in improved form, only to lose to Bertens in the first round.
Then in the rallies, instead of being suckered into trying to out-slug Williams, as some of her other opponents have done, Kerber confounded her by hitting soft balls at sharp angles.
Given their lopsided head-to-head history (Serena leads the series, 9-1) and the fact Williams' last two hard-court losses came against grinding counter punchers Caroline Wozniacki beat her in Miami, 6-4, 6-4, Angelique Kerber conquered her by the same score in Cincinnati last month conventional wisdom suggests that Azarenka should try to extend Serena in longer baseline exchanges.
Surgery and long, tedious rehab would have sapped the spirit of many players – and did not exactly please the young Londoner – but, until she came away from Wimbledon this year, where the world No2, Angelique Kerber, embarrassed her, she had looked too much to her past, she admits.
Kerber dropped her racket on the court and lay flat on her back as Williams walked around the net to embrace her.
When Kerber passed her yet again in the fourth game, Williams turned to her box and mouthed, "I cannot put the effing ball away!" But she held for two-all.
After dropping the first three games quickly, Kerber found her range, and has been unafraid to attack Stosur, taking advantage of her second serve and even Stosur's powerful forehand.
Kerber swung her arms in an exaggerated shrug of frustration.
At 3 3 in the second set, Kerber earned her first break point of the match.
