Early in what would become a tight test of a U.S. Open final, Angelique Kerber sprinted forward to somehow reach a drop shot and scoop a down-the-line winner that landed in a corner of the court.

The Arthur Ashe Stadium crowd roared, and Kerber celebrated by raising her right hand and wagging her index finger in the air, as if to remind opponent Karolina Pliskova and everyone else “I’m No. 1!”

Yes, she is. And a two-time Grand Slam champion, too.

Kerber won her first U.S. Open title and the second major trophy of an out-of-nowhere breakthrough season, taking five of the last six games to beat a fading Pliskova 6-3, 4-6, 6-4 on Saturday.

“It means a lot to me. When I was a kid, I was always dreaming to one day be the No. 1 player in the world, to win Grand Slams,” said the 28-year-old Kerber, who will move up one spot from No. 2 and replace Serena Williams atop the WTA rankings on Monday. “I mean, all the dreams came true this year.”

Never a Grand Slam finalist before 2016, Kerber beat Williams for the Australian Open title in January, then was the runner-up to her at Wimbledon in July. Adding the championship at Flushing Meadows was further proof that all of the changes Kerber has made are paying off.

The better fitness, via extra time in the gym and longer, more intense practice sessions; an improved serve and a new willingness to attack during points, rather than mainly counter-punching, via instruction from coach Torben Beltz; a more positive attitude on court, via help from a mental coach.

“Of course, now everybody will try to beat me and have nothing to lose,” Kerber said. “I will try to take this challenge.”

On Saturday, the No. 2-seeded Kerber trailed by a break at 3-1 in the third set before coming back against the 10th-seeded Pliskova, who hadn’t been past the third round at a major until this tournament.

“It didn’t look good,” Beltz said about the deficit. “But I think that’s also her strength. Because … if she sees she still has a chance, she’s grabbing it and she goes for it.”

Kerber is the first woman from Germany to win the U.S. Open and the first to get to No. 1 since her idol and mentor, Steffi Graf, who got in touch via text message before the final.

It was Pliskova who guaranteed Kerber’s ascension in the rankings by beating Williams in the semifinals, ending her streak of 186 consecutive weeks at the top, which began in February 2013 and equaled Graf’s mark.

Kerber, who collected $3.5 million in prize money Saturday, lost to Pliskova the last time they met, just three weeks ago in the final of a hard-court tournament in Cincinnati.

But at the outset of this final, it was Kerber who was in charge. Her defense is exemplary, scrambling along the baseline to put her racket on seemingly every ball, crouching so low that her knees would come close to scraping the ground.

As she does against most opponents, Kerber would make Pliskova swing two, three, four extra times to try to end a point. And Pliskova was troubled by that in the early going, making 17 unforced errors in the first set alone, 14 more than Kerber. By the conclusion of the 2-hour, 7-minute final, Pliskova totaled 47 unforced errors, 30 more than Kerber.

“With Angie, you cannot wait for mistakes,” Pliskova said. “She doesn’t give you anything.”

Kerber won the toss and elected to receive, perhaps for two reasons- Her serve remains the biggest question mark in a game otherwise full of answers, and it made sense to force Pliskova to deal with an early test of nerves. Either way, the decision worked- Pliskova double-faulted on the match’s first point and got broken from the get-go.

But Pliskova hung in there. And after frittering away her first four break points, she converted her fifth with a lob-volley winner that curled over Kerber and alit right by the baseline. Suddenly up 4-3 in the set, Pliskova turned to her coach up in the stands and yelled, pumping her fists.

Now it was a match, filled with terrific points, tense moments and plenty of emotion. Pliskova served out the second set the only one dropped by Kerber all tournament and spiked a ball. Kerber got broken early in the third and bounced her racket off the court. Moments later, she trailed 3-1.

But this was Kerber’s turn to show some mettle, breaking back to 3-all and again to end it. She dropped on her back after the last point, then climbed into the stands to begin the celebration with her coach and others.

“I mean, definitely, I would say now that she deserves to be No. 1,” Pliskova said. “And after years (when) Serena was there, I think it’s a nice change.”