Rory McIlroy struggled in his first appearance as world number one on Thursday and was sitting seven shots off the pace after a disappointing start to the WGC-Cadillac Championship.
The Northern Irishman mixed four bogeys with three birdies en route to a one-over-par 73 in gusty winds on the Blue Monster course, where it was evident the come down from the adrenalin rush of grabbing the top ranking had started to take a toll.
"It was a bit of a struggle. It was a pretty tricky day but obviously there were good scores out there. I just didn't really get anything going," McIlroy, who earned the number one ranking with his win at the Honda Classic last week, told reporters.
"I thought if I could shoot under par on the back nine, which was the front nine for me, post something around 70, 69, it would have been a good score. But made a couple bogeys early on that nine and couldn't really get it back."
McIlroy, 22, celebrated his arrival at the peak of the sport's rankings by flying to New York where he made a guest appearance during his girlfriend Caroline Wozniacki's exhibition game with Maria Sharapova and he conceded it had been tricky to get back into a groove.
"A little bit. To be honest I felt a little flat out there. I don't know, I shouldn't, it's a World GolfChampionship, but just felt a little flat out there. But, look, I'll go out there tomorrow and try my best, try and get it into red figures and see what I can do," he said.
"It was just hard to get anything going. I mean, physically, I'm fine. But mentally, just I don't know, it's tough. When you're working, you've got, Arizona and you've got a chance to go to world number one and then Honda, you've got a chance to then all of a sudden you're there, and you're like, well, what do you do?"
McIlroy was grouped with the world number two Luke Donald (70) and third-ranked Lee Westwood (76) and the latter really laboured in the wind.
Westwood, who started on the back nine, was unable to recover after recording three of his six bogeys on the opening three holes, while Donald was in contention after mixing five birdies with a bogey and double-bogey.
Australian Adam Scott and American Jason Dufner were joint leaders after shooting six-under-par 66s.