Just when outsiders or even friends think they have a bead on Serena, they're reminded they have no idea. Pendulous swings in her mood, health and level of play have been an overarching pattern in her career. So have long breaks. She defies categorization, and she courts celebrity more than her more introverted older sister, Venus. But they're both rugged individualists and near equals when it comes to talking the sort of zany Williamspeak and non sequiturs they often use to deflect questions.

(Asked recently how she's been able to keep playing this long, 34-year-old Venus didn't cite deftly managing Sjogren's syndrome, the chronic fatigue disease she was diagnosed with three years ago. She said, "Well, wisdom has served me well. I've worn my sunscreen, so I haven't aged terribly. My knees are very tight, not saggy. And the crow's feet have been kept at bay. So I'll give myself an A-plus.")

After resurfacing in Stanford, Serena raised more questions than she's answered about what really happened at Wimbledon.

Longtime friend Andy Roddick said he was so "scared" as he watched her stumble around that he immediately texted Williams because "I grew up with Serena."

Caroline Wozniacki, Serena's best friend on tour other than Venus, said in Montreal, "When you see a friend doing what I saw on TV, I was like, 'What's going on here?' So straightaway, I contacted her." Asked if the scene revived worries of the life-threatening pulmonary embolism and hematoma that Serena battled in 2011, Wozniacki said, "Yes, yes. Exactly. But thankfully, she's OK."

Uh ... she is, right?

"She told me [during Wimbledon] that she was having back spasms, a back problem -- I knew that," Serena's father, Richard Williams, said in a phone interview he granted last week, but only on the condition that he not be asked questions about Serena's relationship with her coach Patrick Mouratoglou, whom she's never confirmed as her boyfriend despite paparazzi photos that suggest otherwise.

And Mouratoglou himself? He shot down speculation that his working relationship with Serena was over just because he said that he hadn't seen her in the two days between her third-round Wimbledon singles upset by Alize Cornet and the doubles incident. He explained Serena was going through "a difficult time," and her sister Isha Price told USA Today that Serena was "sad" and "emotional" after Cornet ousted her.

Once at Stanford, Serena only deepened the mystery by volunteering, "I was scared" and "I still have to go through a series of tests ... just to make sure it wasn't connected to things that run in my family."

What "things"? What tests? She didn't say.

A few days later in Montreal, a reporter's attempt to get Williams to elaborate six minutes into her news conference that started an hour late went like this:

Q: "Do you understand why people found Wimbledon so frightening to watch as you ... "

"Oh," Serena interrupted, reaching immediately to remove a clip-on microphone from her shirt. "We talked about that last week. I think you missed that one. Thank you."

Then she stood up and walked out.

***

The curiosity about Wimbledon might have faded by now if not for the growing consensus that Serena is already the greatest female tennis player of all time, and anything that might derail her career would be huge news.

But at this point, it also seems advisable to suspend any expectation that Williams will fully explain herself. Ever.

Just accept that the authentic Serena is all of what she presents. And leave it at that.

Since turning pro in 1995, Williams has been both an enigma and an unapologetic diva, a famously sore loser and a fun-loving goof who recently posted an Internet video of herself catching scoops of ice cream in her mouth.

She's an iron-willed world-beater who remorselessly craves success. Yet by her own admission, she has sometimes balked at working out like she should and has seemingly been vulnerable to bouts of depression, self-loathing ("I suck right now," she said after her Wimbledon singles loss), sensitivity and anxiety, even apart from life-rocking circumstances such as the 2003 drive-by shooting death of her sister, Yetunde Price, or that embolism that could've killed her if a smart trainer hadn't convinced her to skip an Oscars party and go straight to a Los Angeles hospital.

Upon her return to the US Open in 2012 -- or three years after she was docked the final point of her semifinal match there for raging at a lineswoman, "I'm going to cram this f---ing ball down your f---ing throat," and one year after another fit when she was docked a point for shrieking loudly as she hit the ball on an important point (hardly a unique offense) -- Serena confessed she was almost afraid what would go wrong next at the Open.

Then she beat back both her nagging paranoia and formidable Victoria Azarenka 6-2, 2-6, 7-5 in what Sports Illustrated called the best women's final since a Graf vs. Monica Seles dogfight 17 years earlier.

Typical.

At this point, the only surprise is when Serena doesn't surprise. Sometimes she admits the tightrope walk wears even on her. "I think it would be good to just be like, 'Serena, you have done everything you needed to do. Just have fun and enjoy yourself,'" she told reporters after winning in Stanford.

Part of what makes it all so fascinating is Serena seems to defy that old adage you can't just summon world-class athletic greatness with a flick of a switch. Her power and sensational athleticism will always obscure how she must put in lots of hard work behind the scenes. And that she is smart. And that she has added over the years to her all-around game, not just that serve that many experts rank as the best ever.

But let's be honest: There also are times when she has shown up not in peak form. (Even now, in the midst of her summer tear, her father says, "I think she's trying to lose a little weight.") Then she puts her mind to it and bulldozes most everyone her path anyway.

The only possible conclusion is Serena really is that much better than everyone else. She hasn't pursued greatness with the singular but ultimately self-immolating rigor that caused Bjorn Borg to burn out by 26. But look: Even though she won't turn 33 until Sept. 26, she's already the oldest woman ever to hold the No. 1 ranking, a distinction she's now owned a career total of 202 weeks despite never really bothering to emphasize it much. Twenty-five of her 62 career titles and four of her majors have come in the three years since she "rededicated" herself to tennis after the embolism scare.

"To have this much success late in her career, that's what's most impressive about her to me," says old foe Martina Hingis, a former No. 1 herself.

Williams doesn't indulge in the sheer volume of cut-open-a-vein ruminations that Navratilova was known for, and she's never shown the gravitas that Venus, now the Grand Dame of the tour, has shown on issues such as equal pay or politics.

She's never been tennis' sweetheart the way Evert was. Nor is she the highest off-court earner of her era. That would be Maria Sharapova, even though Williams is by far the more decorated champion. Just not the blond, blue-eyed type that Madison Avenue scurries after.

And yet, if you ask Evert to appraise Serena at this point in her career, Evert says, "I believe Serena is the greatest women's player ever, and I'm honored to be mentioned in her company, and Martina Navratilova's too."

The next thing Evert emphasizes is something very specific that's talked about less: "Our top Americans are mostly African-Americans: Madison Keys, Sloane [Stephens], Taylor Townsend, Vicky Duval, Hurricane and Tornado Black. These girls were around 5 to 10 years old when the Williamses started winning, so it's reflected in this generation."

Golf cannot say the same since the arrival of Tiger Woods.

To Richard Williams, who spent much of spring and summer promoting his memoir "Black and White: The Way I See It," that influence is a particular point of pride.

He always predicted Serena would be even greater than Venus.

He says how it happened isn't a secret at all.

***

She's perhaps the greatest of all time, but Serena Williams has never been embraced the way other former champions were. Al Bello/Getty Images

The backdrop that tennis champions are raised against is often seen as an integral part of their legend. Jimmy Connors was famously raised by two women (his mom and maternal grandma, whom he called "Two Mom") to conquer men. Navratilova defected from communist Czechoslovakia at 18, was outed as a lesbian by 24 and had to carve out a path to greatness on her own, eventually putting together the sort of support team that was mocked in the '80s but is standard today.

In Serena's case, the idea that she will be regarded as the greatest female player ever by the time she's done seems likely, even inevitable. But the way she's likely to be remembered is closer to Navratilova, not Evert: Even folks who are uncomfortable with the details of Serena's or Navratilova's careers nonetheless admire the way they endured.

That's a damn sight different from being unconditionally beloved.

Serena knows this. She even alluded to lacking that feeling after her 2012 US Open semifinal victory set up her first title showdown with Azarenka, when she asked the crowd for help during her postmatch interview, saying, "I'm American, guys. Last one standing. Go USA!" And Venus was even more blunt at the same tournament. After the crowd wildly urged her on, chanting her name during her second-round loss, she said, "Today I felt American for the first time at the US Open."

The first time? It was her 18th year since her debut on tour.

The Williams family is by far the most insular, secretive group to hit tennis since Seles and her tight-knit family. And both the Williams sisters and Seles were highly influenced by fathers who had dislocating experiences early in life.

For Karolj Seles, it was the knowledge of what his father, Jakab, went through as a conscientious objector during World War I.

Richard Williams is unapologetic for instilling a belief in his daughters that they are better than everybody else. AP Photo/Mic Smith

For Richard Williams, it was the horrible racism in the Jim Crow era of his youth in Shreveport, Louisiana, and other places he lived, that informed his worldview. Williams is unsparingly frank in his book about what he endured and the ways he lashed out. He writes a lot about how overcoming that suffering and avoiding bitterness has been the challenge of his life. He says it dwarfs all this fussing of how he prophesized that he'd raise two tennis champions (he dubbed them "Ghetto Cinderellas") after learning the game himself from a man nicknamed Old Whiskey, whom he paid for lessons with pints of liquor.

When it came to raising Serena and Venus with his second wife and co-coach, Oracene Price, all of it shaped the family's approach -- the exterior face they've chosen to show to the outside world all these years, and it's different from their interior life as an African-American family trying to do the unprecedented in a white- and European-majority sport. Richard's generational battle with racism is different from the outsider status his daughters have had to negotiate. But there's still pain and challenges that come with both. For all of them.

Sometimes the Williamses confront this and call things exactly as they see them. When Serena and Venus were booed at Indian Wells for Venus' late withdrawal from a much-anticipated match against Serena and a rival player (Elena Dementieva) suggested Richard fixed the outcome, the Williamses decided never to go back after reporting they heard racial taunts as well.

On still other occasions, the Williamses chose not to even trust others to understand. And that's when you get the elliptical remarks.

"I think we've got a lot of hurt and pain we've been through," Richard said in our phone interview last week. "The only reason I released the book was Serena told me she thought it could help some people. And what I experienced on the book tour was unbelievable. So unbelievable. I finally had to get off that book tour. I couldn't stop the tears from flowing. [Reliving the stories] reminds you of the days you were beaten by white people or had to run for your life. ... And when people came up to me -- black, white, brown, Hindu -- it seemed like that was the only time the tears dried up. I never knew I was accepted so well."

Laughing now, he adds, "I only knew people thought I was crazy."

And now?

"People told me, 'I didn't think the closeness of your family was true. When you first came out, I thought you guys were a joke, pretending how close you are.' But we didn't have to be concerned or pretend," Richard says. "No need to start explaining or apologizing for anything even when people treated us persona non grata.

"If you're trying to be on your way to the top of the hill, there's no reason to go to the bottom of the hill and start over. We don't have to change any opinions. We don't care what anyone thinks. One of the things raising my girls taught me is a kid don't have fear unless they're taught fear. ... Our attitude from the start was we were better than anyone else. And we were criticized hard for that. So hard. Nowadays you see that attitude all over professional sports. But I always believed if you don't believe in yourself, you should not show up. And I did not raise my girls to lose.

"It was: 'We're coming to win.' And we did."

***

Other than her legendary serve, opponents often cite ferocity as Serena Williams' biggest weapon. Timothy A. Clary/AFP/Getty Images

One unchanging truth is sports champions of all eras have great quantities of something. Their individual differences -- even more than the usual similarities they share like a deep-seated hatred of losing -- are fascinating to ponder. What you usually find is what makes a champion isn't just her arsenal of shots.

Evert had a mind and a will that was diamond-hard to crack. On court, she had a vise-like grip on her emotions. Navratilova? She seemed to play serve-and-volley tennis as if guided to the ball a half-step early by some awesome sense of premonition. When it comes to Serena, Pam Shriver, Navratilova's longtime doubles partner and now an ESPN analyst, says: "It's not like Serena has the best forehand or backhand ever, and certainly not the best volley. She is one of the best movers. Just not the best footwork. But when it comes to intimidating power, she's No. 1. Her serve is No. 1, too."

Current players also cite Serena's ferocity. Li Na's coach, Carlos Rodriguez, once spoke about how she seemed beaten before her match against Serena even began. Last year, Azarenka, no competitive slouch herself, vividly described the experience of playing Serena after losing her second straight three-set US Open final to Williams this way: "You've got to fight, you've got to grind, and you've got to bite with your teeth for whatever opportunity you have."

In typical Serena Williams fashion, the world No. 1 has rebounded from her bizarre Wimbledon by winning two titles. AP Photo/Marcio Jose Sanchez

After losing to Serena 7-6, 7-6 in Cincinnati last week, former US Open champion Sam Stosur said, "I think there are probably times in matches I have watched her or even today when you think, 'Oh, there is a little bit of vulnerability there.' But being the champion she is, second serve, she hits it on the line out wide for an ace to give herself a set point in the first set tiebreak. ... More often than not, they come up with the goods to shut you down. It's what happens at the big moments."

Indeed, it has long been noticeable that Serena doesn't make much noise during a match until she feels threatened or cornered. And then? Here come the arm-flailing histrionics and cacophony of sounds -- the grunts, the shrieks, the piercing screams and bared teeth as she bludgeons her groundstrokes and serves, or races to the net to get drop shots and stab volley winners.

That blast-furnace drive is her other greatest trait.

Now granted, Serena's profane harangue at that US Open lineswoman was inappropriate, it's true. But again, let's be real: It wasn't all that different from the obscenities male players from Connors to Ilie Nastase, John McEnroe to Goran Ivanisevic, Jeff Tarango and others yelled repeatedly for years. And they never had to hear bleating that they should get a yearlong ban, as Serena did. Was it different because this time the person doing the yelling was wearing a skirt?

"Serena had the thing with the lineswoman and a few other incidents," Shriver says. "But it's hardly been a usual thing for her. Really, as far as her legacy goes, it's not a big deal."

At tense moments, especially, Serena's will to win just seems to overtake whatever else she's feeling. As German star Andrea Petkovic put it at Stanford, "As long as she has the hunger, we're all basically screwed."

Serena's tear since her Wimbledon meltdown has signaled the hunger is back, heading into this US Open.

As she approaches yet another chance to tie Evert and Navratilova, it's easy to guess what the authentic Serena Williams would say if asked to choose between being regarded as Best Ever or being beloved.

The girl who was raised not to lose at anything would tell you it's both.