Rory McIlroy rued a number of errors as he reflected on a "very disappointing" first-round 74 at the Arnold Palmer Invitational.
McIlroy was in good shape after two birdies and a lone bogey on the outward nine in difficult scoring conditions, although he missed excellent chances at the seventh and ninth either side of a clutch par save at eight.
The world No 3 missed a four-foot par putt at the 10th and worse was to follow at 11, where he drove into a fairway bunker and pulled his second way left of the target and into water, costing him a double-bogey six.
McIlroy almost spun his approach back into the cup at the 13th and tapped in for birdie, but he erred again at the 15th after finding a greenside bunker from the rough and splashed out to 15 feet before two-putting for bogey.
He atoned with a mammoth drive at the long 16th which set up a comfortable birdie-four, but he fell foul of a gust of wind as he hit his approach to the final hole, his ball hitting the rocks just short of the green and ricocheting into a tough lie.
McIlroy failed to save his par as he slipped back to two over par, and he admitted that his wayward long game had been the main factor behind his colourful scorecard.
"It was very disappointing," said McIlroy, who is making only his third start of 2017 following a six-week lay-off with a rib injury. "I didn't hit the ball really the way I wanted, I lost a few shots to the right, put myself out of position quite a few times.
"I was playing okay, I was managing it, and then I felt like I hit two good shots into 10 and walked off with a bogey there. And sort of a bit of a mental mistake at the next, I let that linger a bit, and made double.
"The course is playing pretty tough this year, but even though I didn't play my best I should have shot something under par, I guess. But I'm going to go work on a couple things on the range and hopefully straighten it out.
"My upper body's just sort of outracing the club and I'm leaving the club face open and I just need to square it up. I hit a few better shots on the way in, so I'll try to get a few more of those feelings on the range and try and hit it better tomorrow.
"I didn't putt very well today, I didn't hole much, but my chipping was pretty good, bunker play, that stuff was decent. I just need to put myself in position a little bit more off the tee and if I can do that, then I've got chances to score."