This one mattered. You try not to make too much out of one tennis match, but Serena Williams’ blowout loss to Garbine Muguruza in the second round of the French Open on Wednesday seemed to have a lasting meaning.

To me, it meant this: Williams is never going to dominate women’s tennis again.

You expect your champions to be at their best in the biggest moments when they can be. That’s what Williams had done for years, playing great in majors and trying only intermittently the rest of the time.

This blowout loss was something new. In the big moment, Williams won four games, the fewest she had won in a major.

A 20-year old top prospect is still supposed to be intimidated by Williams, by the moment, the surroundings, the power. Instead, Muguruza, who is ranked No. 35, won 6-2, 6-2, while hitting the ball harder than Williams. She also never showed any fear or intimidation. At the Australian Open in January, it was Ana Ivanovic – who I believe will win this French Open – outhitting Williams. Ivanovic, who had gone a few years without having shown one bit of mental fortitude, never showed fear at facing Williams.

Is there anyone left who is still scared of Serena Williams, other than Maria Sharapova?

Williams is still the best player in the world, and still has the highest ceiling on any given day. She will win more majors. But I don’t see her winning five more to catch Steffi Graf.

Other players are hitting it as hard as Williams now, and they aren’t scared. And in this match, Williams wasn’t moving fast enough to plant her feet or get in position. Muguruza won by throwing the bigger punches, and by hitting right at Williams, who wasn’t quick enough or agile enough to get out of the way.

You see something similar on the men’s tour, too, where mid-level players are figuring out that the way to beat Rafael Nadal or Roger Federer is to grip it and rip it. It forces both of them to play at their best or lose.

And after the match, reporters kept trying to get Williams to explain what had happened, and she just said “I don’t know.’’

“I don’t know.’’

The talk was about the historical aspects of both Williams sisters losing on the same day early in the tournament. It’s true, that rarely happens. But a little honesty here: That’s only because Serena rarely loses early in a major.

Venus, who lost to another prospect, actually cannot be upset anymore. At 34, she can lose to anyone. She still can beat anyone on a good day, too. With her Sjogren’s Syndrome, an autoimmune disease that steals her energy, her body doesn’t do what she wants it to do anymore. Maybe age is playing in now, too. And when she can’t count on her body, that beats up on her mind.

What’s newly evident at this French Open is with Serena. She isn’t invincible anymore.

“I’m going to go home and work five times as hard,’’ she said, “to make sure I never lose again.’’

Not long ago, that would have been enough.

There’s a case to be made that I’m wrong. The slow clay at Roland Garros has always been Serena’s worst surface. On Wednesday, with the sun gone, the clay played even slower. That took away some of Williams’ power.

And she lost easily and early in 2012, too, and then won four of the next six majors. So what makes me think that won’t happen again?

It’s possible. But she has lost her bully-factor. She said her loss was “just one of those days.’’ It’s true that sometimes, especially as you get older, your body just might not feel right one day here or there. But there have been too many of “those days’’ for Williams lately – including last year when Sabine Lisicki outmuscled her at Wimbledon – to count this as a fluke.

It seems strange to say this, but the bully-factor matters just as much in tennis as it does in, say, boxing. Maybe even more in some ways. And when it’s gone, it’s gone. The only place Williams might still have it will be on the grass at Wimbledon. We’ll see.

From here, it’ll still be impossible to go into majors other than the French without predicting a Serena victory. On any given day, she’ll still be the favorite. But there will be fewer and fewer freebies for her, when an opponent lies down before the first point. That means more work, more grinding for Williams, who’s 32. It means fewer wins when you’re having “one of those days.’’

Well, she says she’s going to work five times as hard. That surely sounded scary to Sharapova, anyway.