Beautifully Awkward: Serena and Venus Williams at Wimbledon

The most surprising thing I've ever seen in tennis in person—even more surprising than Serena Williams yelling F-bomb-laced threats at a U.S. Open line judge—came at the famous Bullring court at Roland Garros. It was windy, and the round shape of the stadium and swirling clay made the scene feel mystical, almost like a tornado was about to form.

Venus and Serena Williams were playing doubles together. Yes, no one cares about doubles, and this wasn't even a big match. But somehow, it was beautiful. Stunning. I'm talking about the body language of sisters, the fluidity of their movement as they played together. It's hard to explain, but no matter what one of them did, the other one was in the right spot doing the right thing, offering the right support.

When Venus couldn't keep the ball on the court, Serena knew what to do for her sister. When Serena got upset, Venus knew what she needed. It was like two dance partners, perfectly in sync.

Well, Serena beat Venus 6-4, 6-3 Monday to advance to the quarterfinals at Wimbledon. Believe it or not, it was the first time they'd played each other in a major championship since 2009. And despite her recent upswing, Venus is 35 years old. This match had a feel of finality to it—put bluntly, it was probably the last important match between the sisters. Serena seemed to know as much, and said she looked around and took in the setting.

"It's hard to feel excited,'' she told the BBC after the match. "It's never easy to play someone you love and care about. She's my best friend in the world. I just had to stay focused.''

More than in any of their previous meetings, this match was a test of their sisterhood. Both were in position to take something important from the other. Serena is striving to the best player of all time and is two major titles short of Steffi Graf. Graf also won the Grand Slam, meaning all four majors in one calendar year. Serena hasn't done that yet—but is halfway there this year. Venus was in position to take that away.

Meanwhile, realistically, this was Venus' last chance to win another major. Serena was in position to take that away, too.

Chris Evert, commenting on the match for ESPN, said the sisters kept looking at the court, as if they didn't want to focus on their opponent. And that's hard. Almost impossible. In high-level tennis, you have to focus on your opponent—you have to focus the competitor inside you, the killer inside you, on your opponent. You have to find their weaknesses and take a hammer to them.

Only that's not how Venus and Serena see each other. Never has been.

Granted, this might have been the best match they've played against each other, and unquestionably was the best in a major. At least through the first set, when they were running everything down, crushing every ball.

If there's a single flaw in the mental part of Serena's game, it's that she sometimes loses focus—and interest—against players she doesn't think belong on the court with her. Maybe it's boredom. She looked that way most of last week. Against Venus, she was great again. Serve was great. Forehand was great. Still, things weren't quite right. And the match itself was hardly epic.

Truth is, the sisters have never played a truly good match against each other. Last year in Canada, when Venus won, was the closest. But on the whole, their contests have been more about celebration than competition, about the sheer giddy improbability of their dual rise to the top of the sport, about the novelty and unlikelihood of two sisters being so dominant in such game-changing fashion. And that's OK. Celebration is good. It can be enough. It's a big part of what most fans really wanted and the sport really needed.

But hardcore tennis junkies—and even some people inside the sport—have always had theories about why the sisters' matches against each other are never any good. The dumbest one is that Venus and Serena predetermined the winner before matches, the better to split things up. ESPN's Jason Whitlock joined a long, ignorant line by saying as much last week, claiming that the sisters' father, Richard, picks winners.

That's a crock. Never happened. No chance. How do I know? Easy. Letting someone win is actually an insult in tennis, and Venus and Serena love and respect each other far too much for that.

The other theory is more plausible: Venus and Serena play similar styles of tennis, too similar, and a lack of variety keeps their matches from being interesting. The sisters simply know each other's ins-and-outs too well. Too well to establish any sort of rhythm or flow, and too well for any real drama.

I think there's something to that. As they say in boxing, styles make fights. Still, one of the Williams sisters' enduring legacies is that many players—such as Maria Sharapova—now employ a similar, imitative style. Venus and Serena raised the bar. Others followed. And each sister has played memorable matches against other, non-familial opponents. So it isn't just stylistic sameness.

No, the truth is that the Williams' ugly matches have come from something beautiful inside. In so many ways, the Williams sisters seemed to have mastered sibling dynamics. But on the court, that mastery—the sheer, seemingly well-adjusted nature of their relationship—works against them.

We will never really know what happens behind the scenes in the Williams family. As public as they are, they've kept much of their personal lives personal. But Venus and Serena shared a house for years—and still might. Until a few years ago, they practiced together. They always stood beside their father, whether he was saying something important or something goofy.

I'm sure there was sibling rivalry, probably motivating Serena more than Venus. That's often how it works when you're younger. The older sibling wants to protect the younger one; the younger sibling wants to measure up to the older. But all these years, and we've never once seen them snip at each other? Never once seen them attempt to even get away from each other?

Would you feel that way about you sibling at all times? Be honest.

"I think we've always dreamed, growing up, of playing in the highest level,'' Venus said, "playing each other.''

I'm sure that's true. During all those years practicing together, even when they were little kids in Compton, Calif., an area Venus once called a "ghetto'' with Richard hitting half-dead tennis balls to them out of a shopping cart, they surely thought about Venus versus Serena, Wimbledon final. Or maybe a U.S. Open final.

It happened. They got there. But you wonder if they ever thought the whole thing through, all the way to the end of that Wimbledon final. In the beginning, Richard himself couldn't even watch them play each other, saying that wasn't his vision.

For most of the past decade, the two best heavyweight boxers were brothers Wladimir and Vitali Klitschko. In the documentary "Klitschko'' Wladimir talked about the day his older brother introduced him to boxing. "He hit me so hard, I saw stars,'' Wladimir said. "I thought, `This is not for me.' '' Eventually, they would both become heavyweight champions. But they promised their mother they'd never fight each other. They thought it would break her heart.

It wasn't her vision, either.

Tennis doesn't work like boxing. The Williams sisters didn't have the luxury of avoiding each other. They had to fight, had to have awkward days like Monday, and perhaps a few more to come. Serena can still be the best in the world for a few years, and who knows what Venus will be able to accomplish as she moves into her late 30s. The two sisters pushed each other to the top, and all the while, they just couldn't play a signature match against each other.

Well, maybe that isn't true. Maybe their ragged, uncomfortable contests—marked by an inability to kill each other on the court, to willingly take something from each other—were, in fact, their signature. It was all right there in France, obvious amid the swirling red clay. Venus and Serena belong on the same side of the net.