McIlroy regrets missed chances at British Open
The Northern Irishman, who has not won a major for nine years, ended on six under par, tied for sixth, after four rounds at a drenched Hoylake, seven shots behind winner Brian Harman.
The world number two started his fourth round in style as he hunted down America's Harman but he ran out of steam and two bogeys on the back nine cost him dear.
"Got off to the ideal start again," McIlroy told Sky Sports. "That's sort of been what I've done basically every day, big putt on three and then follow that up with a couple of really well-played holes on four and five.
"It's just hard to keep it going, as you can see out there the conditions are pretty difficult and tricky.
"You can make a few birdies here and there, but it's just very, very difficult to go seven or eight under like I needed today to try to make a charge."
McIlroy, 34, who has finished in the top 10 in seven of his past eight majors, said if it were not for Harman, he would be have been challenging for the title at the Royal Liverpool Golf Club.
"Playing well," he said. "There's nothing else that I can really say. Playing good, keep putting myself in there... but still another really solid performance and still a lot of golf to play this year."