Unforced Errors
Maria Sharapova went into the semifinals of the LA Women's Tennis Championship in 2009 clearly favored to win. Yet, she was beaten by the 10th seeded Flavia Pennetta from Italy. Critics said it was her serve and the recent shoulder surgery. What I noticed during the match was that Sharapova had 61 unforced errors and Pennetta had 23. Unforced errors are mistakes that are supposedly not forced by your opponent. They are mistakes that could have been avoided. Pennetta won not because she played well, but because Sharapova played badly.