BROOKLINE, Mass. – The potent combination of thick rough, slick greens and the pressure of the U.S. Open can take a predictable toll on a player.

Consider Rory McIlroy’s Day 1 at The Country Club. He started on No. 10, made the turn at 2 under par and was a shot off the early lead. Following his victory at last week’s RBC Canadian Open, he was on cruise control right up until the moment he wasn’t, when his drive caught the scruffy edge of a bunker at the short par-4 fifth hole and stayed there.

The 2011 U.S. Open champion was only able to advance his next shot to another bunker and he unleashed his frustration on the sand in a moment of anger.

“You're going to encounter things at a U.S. Open, whether they be lies or stuff like that, that you just don't really encounter any other week. It's hard not to get frustrated,” McIlroy said. “I'm walking up there going like, just come back into the bunker. The thickest rough on the course is around the edges of the bunkers. I was sort of cursing the USGA whenever I was going up to the ball.”

McIlroy hit his third shot 10 feet past the hole and maintained his momentum by making the par putt on his way to an opening 67 and a share of the lead. Learning to deal with, and vent, the bad breaks is all part of the major championship experience, he explained.

“You just have to accept it,” said McIlroy, who was also caught on camera throwing his club after a poor approach shot into the ninth hole. “I gave the sand a couple of whacks because I'd already messed it up so it wasn't like it was much more work for [caddie Harry Diamond], and then I just reset and played a decent bunker shot, and then it was really nice to hole that putt.”

McIlroy also suggested that the pace of play – in particular the group ahead of him that included Scott Stallings, Davis Riley and Victor Perez – didn’t help his mood.

“The guys in front of us were playing so slow. They were like a hole or hole and a half behind the group in front of them,” he said. “That was a little frustrating, too.”