Hantuchova was the stronger of the two early on, breaking away from 3-all in the first set with five straight games and eventually leading 63 42, seemingly on her way to a straight set victory - but Riske clung on just in time, closing in to 4-all. She won the first point of the next game, too, to go up 15-0.
That's when the rain fell and the match was stopped.
"It's never easy, especially when I had those chances early in the second set, to kind of forget it and get ready for whatever was coming," Hantuchova said. "But it was the same thing for both of us."
Riske actually came out of the rain delay better, winning four of the next five games to sneak out the second set and hold for 1-0 in the third. But Hantuchova settled in and calmly ran away with it, reeling off six of the next seven games to close out a two-hour, one-minute, 63 57 62 victory on Ashe.
Hantuchova blasted a 104mph ace on match point - her impressive 15th ace of the day.
"Alison played extremely well at the end of the second set - I'm just really proud of the way I fought back into it in the third, and raised my level when I needed to," Hantuchova said. "Obviously the serve was working really well today. I think that was the main difference throughout the match today."
And when was the last time she served so well? "I guess 11 years ago," Hantuchova said, smiling, referring to her only other quarterfinal here, in 2002. She has now been to the quarterfinals or better at Grand Slams five times, having reached three straight quarterfinals at Wimbledon and the US Open in 2002 and the Australian Open in 2003, and a semifinal showing at the Australian Open in 2008.
But there's something special about this one. "I love New York," she said. "I could live here in one second. I just love the city. It's got so much energy, atmosphere. It's the last Grand Slam of the year. Obviously you always want to finish on a high. I'm really glad I was able to do that so far this year.
"But this tournament is only starting now for me - it means the world to be in the quarters again."
Unfortunately for Riske, her tournament is over. But the American exceeded all expectations here - as a wildcard she made it all the way to the fourth round, having never been to the second week of a major before, and she even recorded her first Top 10 victory along the way against Petra Kvitova.
"I had never been in a moment like that before," Riske said. "She's a seasoned player. She played ball today. So I did all I could for this moment and that's all I could do. She just played too well today.
"But it was a great summer for me. I had a great tournament, even though I did lose today. It was a really great tournament for me. To follow up Wimbledon with something else big was I think really, really cool. And I look forward to playing more tournaments, and playing against the better players."