NEW YORK -- Roberta Vinci clearly took a shortcut into the tennis history books Friday, thanks to her upset of Serena Williams in the US Open semifinals. And that might not seem quite fair.

After all, Vinci hasn't even been in a Grand Slam tournament final -- never mind hoisted the silver at one. Among the four semifinalists at the US Open, Vinci was the lowest-ranked (No. 42). She had the weakest won-lost record (30-20) and had the fewest career titles to her name (9) -- none of them earned since 2013.

Yet she upset Williams and did so with a fetching combination of veteran guile, artisanal shot-making and cool nerves. The performance ended the loser's bid to become just the fourth woman -- and the first since Steffi Graf in 1988 -- to complete a calendar-year Grand Slam. Vinci stopped Williams two matches short of that goal, in exactly two hours, 2-6, 6-4, 6-4.

"I thought she played the best tennis in her career," the devastated loser said of Vinci in Williams' postmatch news conference. "You know, she's 33; she's going for it at a late age. So that's good for her. ... Actually, I guess it's inspiring. I think she played literally out of her mind."

Roberta Vinci's career credentials did not come close to Serena Williams', making the Italian's upset the biggest in history. AP Photos/Seth Wenig

So, unfair? It might seem that way. It certainly hurts, if you're Serena. But look at it another way. On Friday, Vinci shattered one of the most powerful taboos in women's tennis. She beat the dominant player at a late stage in a really big tournament. The disparity in their status is such that you have to give Vinci credit for creating the greatest upset in the history of women's tennis in the Open era.

Few others even come close.

In 1983, 17-year-old Kathleen Horvath upset Martina Navratilova in the fourth round of the French Open. It was the only Grand Slam match Navratilova lost that year. However, it was a quarterfinal, just the second major of the year, and there was no comparable Grand Slam momentum to halt.

Then, in 1984, as Navratilova was on the cusp of completing a "Serena Slam" (winning four consecutive majors), Helena Sukova knocked her out of the Australian Open in the semifinals. (Navratilova ultimately would go on to win the next four majors and bag her sequential Slam.) Sukova was a solid, top-10-quality player who reached four major finals but never won one.

In 1989, 17-year-old Arantxa Sanchez-Vicario upset Steffi Graf to win the French Open. It was a shocker, but Sanchez soon established herself as an elite player. She went on to add three more majors and numerous finals to her résumé. Her success makes that original upset of Graf less stunning.

One of the most memorable upsets occurred in 1994 at Wimbledon. Steffi Graf was the defending champion, but the resolute baseliner from Germany was ambushed by an aggressive American serve-and-volley stylist, Lori McNeil. While the match created shock waves, it was just a first-round battle -- old news by the start of the second week.

Then there was Iva Majoli, who in 1997 clobbered No. 1 and top-seeded Martina Hingis in the French Open final, 6-4, 6-2. Twenty-year-old Majoli wasn't exactly a household name, but she was tearing it up on the red clay that year and heading into Roland Garros as a solid, dark-horse contender. Vinci, by contrast, was an aging, 300-1 long shot just treading water at the start of this tournament.

"It's incredible," Vinci said in her media briefing after the win, repeating, "It's incredible. I'm 32, almost at the end of my career, and then I make the first US Open final in Grand Slam. I didn't expect this. I feel good right now. I can maybe touch the sky with my finger."

On Thursday, Vinci admitted she had called her travel agent to book a flight home to Italy -- with a departure time based on the assumption she would lose to Williams. Now she'll need the ticket to be re-issued.

Had Vinci needed additional motivation before playing, she might have consulted with fellow Italian Linda Ferrando. A journeywoman in the late 1980s and early '90s, Ferrando was unseeded in the US Open of 1990. In the third round, she met the hottest player on the tour, rapidly rising No. 3 seed Monica Seles. Crushed in the first set 6-1, Ferrando reversed the score in the second and stunned Seles in a third-set tiebreaker.

Did Vinci remember Ferrando's upset of Seles? What was the biggest upset in women's tennis history that she recalled, she was asked?

She thought for a bit, cracked a great grin and declared, "Today!"

No argument here.