WHAT HAPPENED: Venus Williams and Petra Kvitova’s highly anticipated quarterfinal under the lights inside Arthur Ashe Stadium was many things – a clash of great feel-good stories, a battle between the only two Grand Slam champions remaining in the women's draw and true theater at its finest, which finished with an appropriate buzz, humming through the air under a closed roof.

So it was only fitting that for the sixth time in the pair’s six-career meetings, the Williams/Kvitova matchup was extended to three sets, and a third third-set tiebreak. But after two hours, 35 minutes, the No. 9-seeded Williams snuck by No. 13 Kvitova, 6-3, 3-6, 7-6, as Kvitova sent a backhand wide to end an absolute classic that may have been the match of the fortnight thus far.

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play video V. Williams vs. Kvitova

“When situations get hairy, it’s crazy out here,” Williams told ESPN’s Rennae Stubbs after the match. “It feels amazing and I didn’t want to let you guys down. Thank you so much for the support.”

That support certainly helped, as Williams’ prospects in the match looked grim. The American earned a 0-40 advantage on Kvitova’s serve while down 2-1 in the deciding set after getting broken in the previous game. But the Czech won five straight points to maintain her lead, and Williams looked like she might have missed her juiciest chance to get back in it.

But in the set’s sixth game, Williams won four points in succession to get back on serve, Kvitova striking a double fault to give back her advantage.

After both player’s held to force the tiebreak, the 37-year-old won six of the first seven points in the breaker to gain a lead that she would not give up, advancing to the US Open semifinals for the first time since 2010.

WHAT IT MEANS: Williams, the oldest player remaining in either singles draw, has already guaranteed that she will finish the year with more Grand Slam victories than anyone else on the WTA Tour - Tuesday’s victory over Kvitova added to one of the more remarkable seasons in recent memory.

Thursday’s semifinal will be Williams’ 23rd at a major, which puts her in sole possession of fifth place in the category since the WTA was formed in 1973.

Williams will also re-enter the Top 5 in the rankings for the first time since January of 2011 by virtue of advancing to the final four in New York for the first time in seven years. The American can reach as high as No. 2 in the world if she goes onto win her third US Open title, and first since 2001.

The semifinal on the bottom half of the draw will be the first All-American semifinal since 2002, as Williams will take on Sloane Stephens, who beat No. 16 Anastasija Sevastova in another intense third-set tiebreak by an identical 6-3, 3-6, 7-6 margin. The two Americans have only met once, with Stephens securing a straight-sets victory over Williams in the first round of Roland Garros two years ago.

Just last December, Kvitova’s career looked to be in jeopardy following a disturbing attack in her Czech Republic apartment. Yet just over eight months later, the 27-year-old reached her first Grand Slam quarterfinal since the 2015 US Open. Kvitova, who remarkably won her second tournament back in June after a five-month layoff, lost in the second round of both the French Open and Wimbledon.

Tuesday’s loss was Kvitova’s second appearance in the US Open quarterfinals, also losing to eventual champion Flavia Pennetta in her first appearance in the final eight in 2015.

MATCH POINT: Venus Williams has defied convention by advancing to two Grand Slam finals already this season? Will she make it three in New York with a victory over Sloane Stephens?