If you were watching the U.S. Open you saw Serena Williams come undone.

Who am I trying to kid? If you were watching tennis, or ESPN, or CNN or even your local news you probably saw the clip.

In a sport where decorum rules the courts it is unusual to see a tennis player throw a fit during a match.

I haven't seen an outburst like that during the U.S. Open since John McEnroe played the game.

It was all over a foot fault. A line judge called a foot fault on Serena and pardon my French, but I believe her exact words were "I swear to God I feel like taking this ball and shoving it down your fucking throat."

Then she continued to point and swear right at the judge.

As in any sport, it doesn't go over well when you threaten the referees.

They hate that.

Now, as much as I appreciate a lady with a foul mouth (and I'm not just saying that, I really do) this paroxysm was completely inappropriate.

Here, see for yourself.

I don't mean to suggest that the line judge wasn't making a lot of unnecessary calls against Serena Williams. She may have been, I don't know, I was watching football, but that is not how a person is expected to behave in a professional tennis match.

This isn't major league baseball, and some people were watching the U.S. Open with their children.

I appreciate her passion but it was misplaced here.

The fit was bad, and embarrassing for Ms. Williams, but that isn't the worst of it. She was docked a point. And that point cost her the game.

...while serving at 5-6, 15-30, the line official called a foot fault on
Serena on her second serve, thus awarding Clijsters double match point,
15-40. However, Serena became upset with the call and began jawing at
the official. To her misfortune, she had already been given a warning
earlier in the match; which now combined resulted in a point penalty,
thus costing her the match.

- Black Tennis Pros

That wasn't all it cost her. She was also fined $10,000 for unsportmanlike conduct.

Serena Williams lost in the semi-finals of the U.S. Open because she couldn't control her temper.

Kim Clijsters won the match on a technicality and went on to defeat Caroline Wozniacki in the finals to win the championship.

To be fair Clijsters is an amazing tennis player. Megan says:

Now honestly, she might have lost the match anyway because her opponent
Kim Clijsters was out playing her and was a couple of points from
winning with the score, 4-6, 5-6, 15-30... Bottom line, Clijsters is a great player and doing amazingly well for
someone who was off having a baby the last three years.  She was
beating Serena on every level and though Serena may have pulled it out
in three, God knows she's done it before, you do the crime, you do the
time.

- Megan's Minute

So maybe Serena would not have advanced, but it stinks to see someone lose that way.

Some people have suggested that it might have been 'roid rage or even PMS. In my opinion Serena Williams is just a fierce competitor. She wasn't playing her best, it looked like she was about to be defeated and she was angry about it. It happens.

Ms. Williams issued a formal statement explaining, if not exactly apologizing for, her behavior during the semi-final match. She is still scheduled to play in the doubles finals with her sister, Venus.

Contributing Editor Sarah also blogs at Sarah and the Goon Squad and MamaPop.