The 33-year-old was knocked out of the tournament in straight sets by Marin Cilic, the world number 16 on Saturday, a loss which extended his failure to reach a final in New York to five years.
It's a long stretch of disappointment for a man who won five successive titles between 2004 and 2008 but whose last appearance in the championship match was in 2009 when he was upstaged by Juan Martin del Potro.
"It's not important to my life," said the Swiss veteran when asked how significant an achievement it would be to capture an 18th major.
"I don't need it to be more happy or anything."
Federer's caution is understandable.
His 17th and most recent Grand Slam title was his seventh crown at Wimbledon in 2012 and even that came after having to wait over two years since his 16th at the 2010 Australian Open.
"The moment itself, it would mean a lot," Federer said.
"I keep working hard to win titles on the tour, not just No. 18," he said.
"I was very happy to get to No. 80 the other week (in Cincinnati, one of three tour titles in 2014), so that was huge for me.
"I'll give it a go again in Australia (next January); hope to be healthy there."
Federer added: "I can't do more than try really hard, which I'm doing."
The Lausanne native was trying to become the oldest winner of a major title in more than 40 years at the US Open, but his record at the Slams is steadily becoming one of diminishing returns.
Although he made the Wimbledon final in July, where he was defeated by Novak Djokovic, his record since Wimbledon 2012 is modest by his lofty standards.
The 2012 US Open ended at the quarterfinals while in 2013 he went to the semifinals in Australia, last-eight at Roland Garros, the second round at Wimbledon and fourth round back in New York.
This year, he was a semifinalist again in Melbourne, fell at the French Open fourth round and made the final at Wimbledon before he slumped out to Cilic in New York on Saturday.
That makes one final appearance in his last nine Grand Slam outings.
He almost even didn't get that far, coming back from two sets to love down and saving two match points against Gael Monfils in the quarterfinals.
"I'm happy that grass can grow over this, even though I'm not too disappointed in the sense that I think this match gets forgotten very quickly," Federer said.
"I just think conditions were fast; he served great — it was one of those matches like old school tennis," he said.
"It was just full swing from all sides: forehand, backhand, serve, return."
Federer said he wants to move on, with a chance ahead to win one of the few honours missing from his collection — the Davis Cup.
Next weekend, Switzerland host Italy in the semifinals in Geneva in front of an expected 18,000 fans.
Federer and Australian Open champion Stan Wawrinka will be hot favourites to take their team to a final date against either France or defending champions Czech Republic.
"I'm looking forward to be playing at home, especially after the run I have had of late," said Federer before adding ruefully, "I really felt like I could win this tournament."