Golf is the individual sport where, they say, you can’t win a tournament early, but you can certainly lose it. With a cumulative scoring system, the adage makes sense.

For one match, at least, that cliché applied to tennis. Ana Ivanovic led Serena Williams 3-1 in the first set of today’s Cincinnati final and had three chances to earn a double-break advantage. Like she did during her upset of Williams at the Australian Open, Ivanovic was tagging returns for winners and terminating rallies with an arresting set of groundstrokes. When Ivanovic’s game is in sync, it might be the most beautiful to behold in the WTA.

At the same time, the lethargy that has been lingering around Williams of late persisted. She looked fatigued, more so than Ivanovic, who had completed a marathon semifinal with Maria Sharapova late last night. And Williams’ serve, which looked like an impostor in her taxing semifinal win over Caroline Wozniacki, continued to misfire.

But when Ivanovic’s lead shrank to 3-2 instead of expanding to 4-1, this entire match—and tournament—changed. If there wasn’t a mental shift, there was an evident change in physicality, which would manifest itself on the scoreboard. Williams would serve cleaner, become the aggressor in rallies, and deny Ivanovic any semblance of an opening the rest of the way. Essentially, the Serena Williams we’ve come to know had reappeared. Ivanovic would win just two more games in her 6-4, 6-1 loss.

Ivanovic’s strong start had one unintended consequence: It forced Williams to serve harder. “I just kind of close my eyes and serve…I don’t think about it,” she said after winning, incredibly, her first ever Cincinnati title. “I think when you think too much it gets crazy.”

Williams’ comments were meant as a response to a joking remark made by the runner-up, who asked the world No. 1 for some serving advice. But they are perhaps the only way to explain her sudden turnaround. Williams’ serve, which defined this match as much for her as it did for Ivanovic, became the smoking gun we’ve known it to be, giving her added room during subsequent rallies. Under early pressure, Williams was forced to take more chances; in the second set, that was Ivanovic’s task, and she wasn’t able to sustain the level of excellence needed to combat her legendary opponent.

At 1-1 in the second set, Ivanovic got to 0-30 on Serena’s serve—and nearly 0-40, with a forehand return that just landed wide. But the Serb’s eventual errors came at just the wrong times, while Williams’ winning serves were particularly timely. Both trends lasted until the trophy ceremony; in retrospect, it was Ivanovic’s last push.

By the end, Williams was in full flight. That’s another adage we often associate elsewhere, typically with Roger Federer, who will attempt to win his own Cincinnati title this afternoon. But there was no other way to describe this vintage version of Serena Williams, one we’ve seen too few times this year—yet one you recognize instantly when you see it.