From the Official website of the Australian Open: "As if losing in the opening round on a blazing hot day wasn’t bad enough, world No.65 Rebecca Marino was then requested to provide a routine anti-doping sample..."
Again, if the test distribution plan is on taking samples from losing players directly after matches (see 2009), there should be little surprise that there are so few positive tests for steroids, synthetic testosterone, EPO, stimulants, etc. You name it. They aren't going to find any.
At a minimum, the testing of match winners at random times on off-days is required.