SERENA PENALTY: 3%

Serena Williams was fined $10,000 Sunday for a profanity-laced tirade directed at a U.S. Open line judge, and an investigation is under way to determine whether there should be additional punishment.

The $10,000 penalty — not quite 3 percent of the $350,000 in prize money Williams earned by reaching the semifinals at Flushing Meadows — is the maximum on-site fine that can be issued for unsportsmanlike conduct at a Grand Slam tournament.

The U.S. Open said in a statement that the Grand Slam Committee Administrator will "determine if the behavior of Ms. Williams warrants consideration as a major offense for which additional penalties can be imposed."