McIlroy’s round included two birdies, a double-bogey and a quadruple-bogey at the par-4 11th hole, where he bent his wedge in frustration after hitting a ball into the water.
"I just hit a bad tee shot into the creek there, and then what you don't want to do as a golfer is follow one mistake with another, and that's what I did," McIlroy told reporters. "And obviously I got a bit frustrated.
“I think that's what this tournament does to you. At one point or another, it's got the better of you, and it definitely did this weekend."
Continue Reading Below
The No. 2-ranked golf player in the world said that the pin locations on Sunday were on the "edge" of being unfair. "I can see the [USGA] trying to protect the scores and stuff," he said. "But the pin position on seven today, for example, was on the back of a slope. "At least put it a couple of yards down so it's on the flat part of the green. They decided to put it on a ridge. It's a U.S. Open."
McIlroy finished in a tie for 41st at 14-over par.
Meanwhile, 32-year-old Englishman Justin Rose bested six-time U.S. Open runner-up Phil Mickelson to win the tournament with a level-par 70 to end one over.
Rose led the group by one going up the difficult 18th and hit a fantastic four-iron approach to set up a par four. Meanwhile, Mickelson tied for second with Jason Day, finishing 3 over par, two strokes behind Rose. Mickelson bogeyed the 13th, 15th and 18th holes on Sunday and double-bogeyed Nos. 3 and 5. He finished with a final-round 74, his worst of the four days in the tournament.