By Steve Ginsburg
"It was a tough match," Federer said after the two hour, 40-minute affair at on a warm but blustery day in Arthur Ashe Stadium. "Coming in I knew it was going to be tricky and I'm happy that I was able to counter his pace and his good play."
Cilic, the lanky 27th seed, had his chances but could convert only two of nine break-point chances against the third-seeded Swiss.
"Definitely his serve keeps him in there all the time," said Cilic. "And today he was, in those crucial moments, finding a way to make the game a little more difficult for me to read what he was going to do."
The Croat double-faulted to give Federer a 5-4 lead in the third set and never recovered. He had just received a time violation by the umpire prior to his costly error.
"The only thing I'm not happy about is that referees are not consistent," he said. "I'm not saying they were wrong, they should just be more consistent with the other players."
Federer conceded the timing of the violation took him by surprise.
"These time violations come out of nowhere sometimes and then they'll never come back again," he said. "If he was really taking too much time it's correct that you warn a guy but then you should just stay tough and also go to point penalty.
"Marin was playing pretty quick, like I was. It was a tough call."
When asked how he was progressing through the tournament the 30-year-old Swiss said, "I'm on track because I'm in the tournament."
"That's the most important at the end of the day," he said. "I seriously don't care how I'm playing. I wish I play my best every single time and feel amazing. That's not reality.
"That's what the beauty is of this game is, trying to find a way when you're not feeling great."
In the round of 16, Federer will face either Argentine Juan Monaco or Tommy Haas of Germany.
By advancing to the fourth round, Federer became the fourth player to qualify for the season-ending ATP World Tour Finals in November.
"As long as I'm in the tournament I know I have a shot, and that's what it's about right now," he said.
(Editing by Larry Fine)