As good as she’s been this year, Iga Swiatek came to the US Open unsure of what to expect.

She complained that women use different, slightly lighter, tennis balls than men do at Flushing Meadows, where she’d never been past the fourth round. She was trying to grow accustomed to the noise and distractions, the hustle and bustle, of the Big Apple. And she arrived with a record of just 4-4 since her 37-match winning streak ended in July.

None of that matters now. Cementing her status as her sport’s new dominant figure by winning what is expected to be the last tournament of Serena Williams‘ career, the No. 1-ranked Swiatek outplayed No. 5 Ons Jabeur 6-2, 7-6 (5) in Arthur Ashe Stadium on Saturday to claim her first championship at the US Open and third Grand Slam title overall.

The 21-year-old from Poland won the French Open for the second time in June and is the first woman since Angelique Kerber in 2016 to collect two major titles in a single season.

“She’s really set the bar very high. It’s great for our sport,” said Jabeur, a 28-year-old from Tunisia who will rise to No. 2 in the rankings on Monday.

She is the first African woman and first Arab woman to reach a Grand Slam final and was participating in her second in a row. But she is 0-2 at that stage, being the runner-up at Wimbledon in July.