Roger Federer tied Andre Agassi for the second-most match victories in Grand Slam tournaments by beating Santiago Giraldo in straight sets on Monday.
The third-seeded Swiss won 6-4, 6-3, 6-2 to move level with Agassi on 224 singles wins at tennis majors; nine behind Jimmy Connors.
Federer said he wasn't aware of that mark.
"I've played many Slams in a row already. I'm healthy. It's just another way of saying, 'Roger, you've been doing many right things throughout your career,'" he said. "It gives me good satisfaction and points me in the right direction."
Federer improved to 12-0 in first-round matches at Flushing Meadows, and 57-6 overall at a venue where he's lifted the champion's trophy five times.
The Swiss star, who turned 30 on Aug. 8, is trying to win at least one Grand Slam title for what would be a record ninth consecutive year. He also would like to become the first 30-something man to win a major tournament since Agassi at the 2003 Australian Open.
Federer has won each major trophy at least once, so he knows the ins and outs of the various Grand Slam surfaces - the hard courts at the Australian Open and U.S. Open, clay courts at the French Open, and grass courts at Wimbledon - and was concerned organizers have made the Flushing Meadow courts too slow this year.
"Did they make a mistake? Maybe they did paint the court a bit too rough. It's just unfortunate that maybe all the Slams are too equal," the 16-time major champion said. "They should feel very different to the Australian Open, and now I don't feel it really does."
He showed a few signs of rust early under the lights against Giraldo, losing serve three times in the first two sets. Federer thought that might have been connected to his sense that the court played "definitely slower" than at the hard-court tuneup tournaments at Cincinnati and Montreal this month - and slower than in New York in 2010.
"It takes some getting used to. You're not getting as many free points with your serve," Federer said. "Maybe that was part of the inconsistent play I had early on in the first couple of sets."
Explaining how the conditions felt Monday, Federer said: "The night session just feels like you can take huge cuts at the ball, you can run everything down. It's great for tennis, but I'm not sure if it's really what the game needs. The game needs different speed at Slams and so forth. I don't feel we quite have that at the moment, especially if the U.S. Open is getting slower."
On the other hand, Federer noted that he thinks that will lead to "amazing points."
"It's going to be super athletic, which is fun," he added. "So it's all good."