Cw

If the last month has taught us anything, it’s that tennis, even in the era of the dominant men’s top tier, is still a game of days. As in, each day is a new one, and you’re not going to perform the same way in all of them. One day Roger Federer can turn the tables on his nemesis, Rafael Nadal, only to have them turned on him at the next event by a player he has always owned, Andy Roddick. And the very next day Roddick, after playing with newfound aggression against Federer, can fade back into the woodwork behind the baseline and lose in a hurry to Juan Monaco. The Masters events of March are especially good at reminding players and fans not to get ahead of themselves. In these compressed events, one big match just leads to another 24 hours later.

All of which is to say that we also shouldn’t get ahead of ourselves when we talk about Caroline Wozniacki’s career-best performance against Serena Williams in Miami last night. Yes, she brought a kill-or-be-killed mindset, an aggressive backhand, and a potent body serve with her in her surprisingly straightforward and convincing 6-4, 6-4 win over the 13-time Slam champ. But Wozniacki isn't known for any of those things, and they could disappear tomorrow, the same way that the proactive attitude that Roddick showed off at night against Federer evaporated in the Miami sun against Monaco the next afternoon.

So there’s your caveat, in case a different Caro shows up against Maria Sharapova in the semis. Still, it must be said that Wozniacki’s win over Serena had the feel of a career-changer. Not because she’s going to play that way every day; habits are harder for a tennis player to break than they appear to be from the outside, and comfort zones are comfort zones for a reason. As much as players may consciously plan to leave them behind before a match, as much as they may try to play farther up in the court, or take the ball earlier, or hit it flatter, or follow it to the net, they tend to gravitate back to what they like to do or where they like to play as a match goes on, and especially when it gets close. The entire world, including her father on changeovers, has been urging Wozniacki to take charge of rallies, use her backhand to attack, and go after her serve, but she’s more comfortable with safety and consistency. Breaking a habit requires that you think, rather than just react, on every point and every shot, and that’s not easy for anyone.

There is one time when it’s easier, though—when there’s no choice in the matter; when a player knows that he or she must play differently or they’re guaranteed to lose. That’s what inspired Roddick to bring the heat on his forehand in the third set against Federer, and it’s what inspired Wozniacki to get creative against Serena. Wozniacki, and her father, knew there was no choice. Afterward, she was asked what her dad said to her when she called him on court.

“He just said, you know, go for it. Don’t think about the score. If you make a mistake, doesn’t matter, But don’t just put the ball back, because you won’t have a chance.”

Nothing frees a player up more than hearing that they’re errors won’t matter. Or that getting the ball back is the surest way to lose a match rather than win it.

That said, this version of Wozniacki—she looks leaner than ever—didn’t blow Serena off the court or throw all caution to the wind. Afterward, she said the most important thing was that, "I didn't make too many unforced errors and I made her run." In other words, consistency was still at the top of her mind.

But Wozniacki's performance was impressive for its tactical guts and timely variations. She surprised Serena and put her on her heels with body serves on important points. She also surprised her, and hit winners past her—never an easy thing to do—by wrong-footing her. Serving for the set at 5-4, 30-30 in the first, Wozniacki broke her usual pattern with a nice down the line forehand that Serena didn’t anticipate. In the second set, she held onto serve by breaking her usual pattern with a sharply angled crosscourt backhand. Again, Serena wasn’t ready for it. Finally, serving for the match a second time, at 5-4 in the second, with Serena gathering momentum fast, Wozniacki again won a key point with a flat serve to the body.

Williams said afterward that her game was at “20 percent.” She wasn’t at her best by any means, and if she’d avoided just a couple of costly errors in the second set, the result might have been different—she probably wasn’t going to lose a third set to Wozniacki. But this wasn’t a match where Serena was bad all on her own. Wozniacki kept surprising her, kept making her make balls, kept her guessing.

In earning her first win over Serena Williams, Wozniacki showed herself that she can leave her comfort zone and succeed, and hat she has weapons other than defense and tenacity at her disposal. But for the first time in a while, she also showed the world again why she has gotten as far as she has in the first place: She's tough. Self-belief has never been a problem with her, but it’s also never seemed so obvious an asset as it did last night. Yes, she was broken while serving for the match at 5-2, but she didn’t let the moment scare her. What she's lacked belief in is the type of game she played last night. If anything, beating Serena should show Wozniacki that she doesn’t have to change her game that much to make it more effective. But if she wants to win Slams, she has to treat them the way she did this match—as if she has no choice other than to "go for it."

It was just one day in a game that's made up of thousands of them, but whatever happens next, it was a day that Caro shouldn't forget.