After winning the prestigious Orange Bowl junior title at age 15, she said, she wrote herself a check for the amount that went to the U.S. Open winner that year.

She still has the check. “Ever since this moment, I just kept visualizing that,” she said. “If that can happen on Saturday, then that would be pretty cool.”

Tennis has a habit of shrinking the concept of a generation: Roger Federer versus Rafael Nadal was once viewed as the old guard versus the new, although they are less than five years apart in age.

But this U.S. Open women’s final will be an intergenerational duel by any definition.

Williams will turn 38 this month. Andreescu turned 19 in June and had not yet been born when Williams stormed through the singles draw in New York in 1999.

This will be the biggest age gap in a women’s Grand Slam singles final in the Open era, which began in 1968. The gap is more than a year wider than the 17 years 45 days that separated Martina Navratilova from the teenage phenom Monica Seles in the 1991 U.S. Open final, won by Seles. Just a year ago, there was a 16-year gap as Williams lost to 20-year-old Naomi Osaka in an Open final.

Williams, the oldest women’s Grand Slam singles finalist in the Open era, has clearly redefined what constitutes a tennis grande dame with her late-career success. Coming back after giving birth to a daughter in 2017, she has reached four of the last six major singles finals in her so-far unsuccessful quest to match Margaret Court’s total of 24 titles.