There might be a reason that Serena Williams keeps her public comments close to the vest. She has had people in her life talk without reservation for her.

First, Williams' father Richard spoke his mind, perhaps creating an "Us against the world" mentality for Serena and older sister Venus.

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Now, her childhood coach has come out publicly and talked about her will to win as a good-vs.-evil balance, according to complex.com.

"... The one thing about Serena that always stood out with me was that she was fearless, said Rick Macci, owner of Rick Macci Tennis Academy in Boca Raton, Fla. "She wasn't afraid to miss. And she hated to lose. She had to be the first in everything, even if it was getting a drink of water.

"I could remember playing tag with all the other kids in the sand pit. Just to work on agility, dexterity, you know. When she played tag, she played with a closed fist.

"That's how competitive this girl was. I told Richard one of two things was going to happen: She will be No. 1 in the world, or she will go to jail. One [of those] two things can happen. And I'm serious."

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Macci didn't elaborate on how her competitive nature might've led her to the dark side, but he did compare her will to that of Michael Jordan, saying her mental toughness is one of her biggest assets.

He conceded that Williams always has played under tremendous pressure.

So it stands to reason that her quest for the calendar Grand Slam grinded to a halt in the U.S. Open semifinals in part because of her nerves, though she won't admit it.

Macci then added that he thought Williams is the greatest women's tennis player of all time right after he called the current state of women's tennis "diluted" because of injuries and past retirements.

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