Ask Serena Williams what could prevent her from completing tennis' first Grand Slam in more than a quarter-century at the U.S. Open and the response will not include the name of a single possible opponent.
"Well," she began when that question was posed, "I'm always one of my biggest competitors. I can always stop myself, so that's why I kind of just try to stay positive on the court and stay really focused and stay as calm as I can."
"I have to make sure I'm good physically," Williams said.
Anything more to worry about?
"Fear and doubt can stop me, too," she continued. "If I step out on the court and I'm a little nervous or I'm fearful, then that's never a really good sign."
Really? That happens?
"It does happen. But I just embrace it and I bottle it up, and I throw that bottle away," Williams said. "And I just go for it."
Already considered by many the greatest female tennis player and among the greatest athletes ever — no matter the gender or era — the 33-year-old American has become adept at discarding that fear and doubt. When the U.S. Open begins Monday, Williams, seeded No. 1, will embark on a bid to become the first player since Steffi Graf in 1988 to win the sport's four majors in one season.
Only five players have won a calendar-year Grand Slam; the last man to do it was Rod Laver in 1969.
More is on the line as well. Williams can equal Graf's professional-era record of 22 major singles titles (13 of Margaret Court's 24 came against amateurs). She can become the first player in the Open era (since 1968) with seven U.S. Open trophies and the first woman since Chris Evert nearly 40 years ago with four in a row.
Mostly, there is the Grand Slam to chase.
"When I was younger, that was definitely a goal of mine, to win a Grand Slam," Williams said. "It's become more of, like, a distant dream, fable, kind of thing. … I've never been this close, so we'll see."
Here's the question 127 of the 128 women in the Open's main draw are asking themselves: How do you beat Williams?
A solid return helps, as can the occasional free point off a big serve. So can an ability to hang in there at the baseline on extended groundstroke exchanges. And clearly, it helps to have an off-target performance from Williams, who has been dealing with a problematic right elbow.
Still, women who have beaten her pointed to a positive mind-set as the key.
"You have to believe that you can (win)," two-time Wimbledon champion Petra Kvitova said.
Kvitova, seeded fifth, is responsible for one of Williams' two losses in 50 matches in 2015, on red clay at Madrid in May. Williams' other loss was against Swiss teenager Belinda Bencic on a hardcourt at Toronto this month.
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"You know you have to play great to beat her," Kvitova said. "Even if she is not playing well, we've seen her come back. Opponents know it's not (over), even if you are leading."
As for what general advice she would give someone facing Williams, Kvitova laughed and responded: "I'm going to keep it to myself."
Williams' most recent Grand Slam loss was June 2014 against Alize Cornet in Wimbledon's third round. Afterward, Cornet said: "When she plays someone who finds the right tactics, she looks a bit lost on the court. In my opinion, there are more and more players understanding how to play her."
Williams is 28-0 at majors since. Reminded of that declaration, Cornet, seeded 12th at the U.S. Open, chuckled and said: "I guess, maybe, I was wrong."