After another early exit at Indian Wells, it is clear that the Australian has lost all confidence in her game.
She has a very stable team behind her, but she does go through periods where she really seems to have nothing to offer.
It happened last year - the Australian Open in 2011 was a disaster as she just could not cope with the hype - and despite taking that big step in New York, she is still not right.
I don't see anything wrong with her tennis at all, but she seems flaky mentally and she needs a couple of good tournaments to get herself back on track because at the moment she is getting turned over by players who, for the best part of last year, she would have beaten in her sleep.
It is surprising that the US Open victory didn't solve her confidence issues though. Her second consecutive flop in Melbourne is understandable because there is so much thirst for her to succeed in Australia that anybody would find it difficult to cope, but I didn't think that would carry on to regular WTA events.
It has now got to the stage where it is a cause for concern, but she is also the type of player I could easily see getting quickly back to the level of a top five player once she gets a few big victories under her belt.
She just needs a couple of good tournaments, I'm not ready to discount her for Roland Garros just yet because if she could just rediscover a hint of form before arriving in Paris, then she will still be a danger.
More worrying for me than Stosur, is Caroline Wozniacki's form this season. I do believe it is going to be a very tricky year for the Dane.
I do not see any improvement in her game from last year and now everyone else goes out on the court feeling that they can beat her and I can see her ranking spot being put under real threat.
Wozniacki faces Ana Ivanovic in the early hours of Wednesday morning in what should be a really great match. Ivanovic suffered a similar slump to Stosur after winning her first Grand Slam title (the French Open in 2008) but I'm seeing signs now that she is rediscovering some of that quality that made her world number one in the past. I'm really excited by her at the moment.
Ivanovic seemed to be struggling a bit at the end of her victory against Ksenia Pervak, and for a moment I was worried she might have contracted the stomach bug that has been sweeping the tournament, but if she is feeling okay, I think she will beat Wozniacki which would be a big statement about where both players are at the moment.
I'm not reading too much into Andy Murray's surprise early exit in the men's draw. These things happening from time to time and it is probably no coincidence that he also played his worst match of 2011 when he lost to Donald Young in the second round.
Certainly, I think he is hampered by the conditions in Palm Springs. The court is very slow there, even if the ball does fly in the air, and it is difficult for him to get into his usual rhythm. Guillermo Garcia-Lopez is a fine player on his day, but Murray has dealt with him comfortably in the past.
Of course, I was surprised by the result and it didn't look very good. You could see Murray was genuinely shocked by the defeat and couldn't account for it and to be honest nor could I or anybody else for that matter.
But I don't see it as part of a pattern or anything, you just have to accept that at times there will be blips along the way.
This gives him a chance to get to Miami a bit earlier than planned and there he can work on some things with Ivan Lendl. He's also got a home there, so will feel very comfortable with his surroundings.
So while he will be bitterly disappointed with the defeat, in some ways it might even serve as a blessing in disguise.
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