New York - Youth may be wasted on the young and so it seems is the US Open, where four of the men's quarter-finalists are over 30 and two more have already celebrated their 29th birthdays.
This year's New York showpiece featured a record 40 men over 30 in the first round, up from 32 in 2014.
The oldest was evergreen German Tommy Haas, the 37-year-old who was playing in his 17th US Open.
There were 10 teenagers -- the most since the 12 which featured in 1990 -- but only two survived until the second round.
No man born in the 1990s has won a major.
Roger Federer is the oldest man left. The 34-year-old five-time champion is due to face 29-year-old Richard Gasquet on Wednesday for a semi-final spot.
The 17-time Grand Slam title winner is playing in his 64th consecutive major, a run stretching back to 1999.
He believes his longevity is a result of making drastic changes to his schedule a decade ago.
"The idea was always trying to be around the game for a long time. And for that in 2004 when I became world number one, I took a decision with my fitness coach at the time that we're going to plan long term," said Federer.
"Sure, we can chase money or more tournament victories. We can play more frequently, more often, train harder.
"But we decided we will try to stay around 20 tournaments during the year, which is a lower number.
"If you look back, Yevgeny Kafelnikov used to play 30, 32 events back in the day. I said that's not something I really want to do."
Coming into New York, Federer had played just 12 tournaments in 2015, winning five titles, and skipped Switzerland's defence of their Davis Cup title.
World number one Novak Djokovic, the second youngest quarter-finalist at 28, had played one event fewer, capturing six titles.
Haas's career has been plagued by injury, but he believes the physical strength of the older players is keeping them at the top of the game.
"A lot of things have changed with technology. Seems like sometimes the surfaces are a little bit slower, balls are getting heavier," he said.
"It's gotten a lot more physical. Everybody is getting more fit, bigger and stronger and hitting with more velocity, more spin."
The second oldest quarter-finalist is Feliciano Lopez, who will be 34 on September 20.
He has made the last-eight for the first time in 13 attempts.
He faces Djokovic while, in the same half of the draw, 30-year-old Frenchman Jo-Wilfried Tsonga, in his second career quarter-final in New York, takes on defending champion Marin Cilic, the baby of the eight remaining men at 26.
The last time that four or more men over 30 made the quarter-finals was in 1982.
Kevin Anderson, who put out third seed Andy Murray in the fourth round, is playing his first Grand Slam quarter-final in his 27th major.
The big South African will be 30 in May and he puts his late success down to a belated start to his professional career.
He only turned pro in 2007 at the age of 21 after studying at the University of Illinois.
"My body's holding up great. I really do as much as I can to take care of myself," said the Johannesburg-born, Florida-based Anderson, who faces 30-year-old French Open champion Stan Wawrinka for a semi-final spot.
"Going to college and turning pro a little bit later, I always felt myself a little younger than maybe some of the other guys my age who have been on the tour a little bit longer."
He added: "Just watching Roger playing at 34, just moving incredible.
"I'm still improving. My desire is still there. Right now I don't think age is something to worry about."