Life-long friends Roberta Vinci and Flavia Pennetta as well as Daniela Hantuchova reached the US Open quarter-finals to ensure five women over the age of 30 will be in the last eight.
Vinci, the 10th seed, beat compatriot and qualifier Camila Giorgi 6-4, 6-2 to reach the quarters for a second successive year yesterday.
Pennetta, now at 83 in the world, made the last eight for a fourth time with a 6-2, 7-6 (7/3) win over Romanian 21st seed Simona Halep and will tackle childhood friend Vinci with a place in a major semi-final for the first time at stake.
Slovakia's Hantuchova, who last made the quarter-finals as a teenager in 2002, saw off American wildcard Alison Riske 6-3, 5-7, 6-2 on the back of 15 aces and 46 winners.
"Roberta and I shared a room for four years. She's like a sister," said former world number 10 Pennetta, who splits a 4-4 career record with Vinci.
"I think it's going to be a really tough match for both of us. We know each other really well. I have known her for 20 years or more, we lived just 35, 45 kilometers away from each other.
"So is going to be really nice for us because one of us is going to have the chance to be in the semi-finals."
Monday's events were hard luck on Halep, who came into the tournament having won four titles on the tour this year. She was hoping to be the first Romanian in the quarter-finals since Irina Spirlea in 1997.
Halep was serving at 5-4 in the second set with a set point when torrential rain caused a suspension of play for more than four hours.
When they returned to the Louis Armstrong Stadium court, Halep's composure was shattered and Pennetta hit back before racing through the tie-breaker for victory.
Vinci recovered from 1-4 down in the first set to race away with 11 of the next 13 games to beat world number 136 Giorgi, who had stunned former number one Caroline Wozniacki in the third round.
Hantuchova and Riske were at 4-4 in the second set when they went off for rain.
"The rain didn't make it easier on both of us but I'm glad to be into the quarter-finals," said Hantuchova, whose best Grand Slam performance was a run to the Australian Open semi-finals in 2008.
"In every match I'm giving my heart into it. It might not be the best tennis but I'm trying my best."
The 30-year-old Hantuchova, now down at 48 in the world after being as high as five in 2002, will face either world number two Victoria Azarenka or Serbian 13th seed Ana Ivanovic for a place in the semi-finals.
That match was pushed back to Tuesday as more than 30 matches were wiped off the program due to the rain.
Vinci, Pennetta and Hantuchova joined Serena Williams and Li Na as the players over 30 in the quarter-finals -- the most in the Open era since five also made the Australian Open last eight in 1977.
"Camila played so flat but I served really well and won lots of points that way," said Vinci, who completed business just before the deluge hit New York.
She was helped by seeing Giorgi's game completely fall to pieces on the Grandstand court as the 21-year-old hit seven double faults and 35 unforced errors.
"Camila is a great player and had nothing to lose after winning three matches in qualifying and three in the main draw. She is one for the future.
"I had lots of points to defend so I am happy to get to the quarter-finals again," added Vinci, who will make the world top 10 if she wins her next match.
Despite defeat, Giorgi, who missed the entire hardcourt season in the run-up to the US Open with a shoulder injury, was content with her performances in New York, which will guarantee a return to the world top 100.
"It wasn't my day. I didn't play good," she said. "It was a great week coming back from two months without playing and I played a really good level."