I don't think Serena gave any bogus injury excuses when she lost to Sabine Lisciki at
Wimbledon or Virgine Razzano at French Open. I don't think she always claims an
injury after a loss. There is also corroborating evidence here. We all saw how she
moved during the match, she quit doubles, did not practice before this match
and so on.
But, then one might ask, why did she play? Hey, you never know, she thought
she might have been able to pull it off despite the injury. After all, they claim
that she was in more pain in the match against Hantuchova which she won
in straight sets. Also, they say, this is temporary and she expect to fully
recover in just a few days. So, if she had managed to win against Anna,
the back pain might have gone away in a couple of days and she might
have become a contender.
However, she may say the match was on her racquet and she lost it rather than
the opponent won it sometimes. That is ok with me as Champions need to have that
belief.