The world No 1 is expected to be fined by the PGA Tour following his remarkable display of temper at the par-five eighth hole, where he turned an excellent birdie chance into a bogey-six.
McIlroy had got off to an encouraging start with birdies at the first two holes, but he bogeyed the next after blocking his tee-shot into water and he then took three putts from short of the green at the short fourth.
He got back on track with a 25-foot birdie putt at the seventh, and he found the fairway at the eighth and took dead aim with a three-iron from a little over 220 yards.
But he tugged the shot way left of the green, and the ripples in the lake had barely subsided when he angrily hurled the offending long-iron into the water before composing himself ahead of his fourth shot.
McIlroy managed to find the green and two-putt for a six to limit the damage, and he responded positively with birdies at 10 and 12 only to give one back at the 14th after he lipped out from five feet for par.
He bounced back again to convert a fine approach to the 17th, and a closing par capped a 70 which left him eight shots off the lead on one under heading into the weekend.
McIlroy revealed afterwards that he was still bothered by missing the cut at last week’s Honda Classic, while being a little out-of-tune with his swing also contributed to his club-throwing antics at the eighth.
“Frustration got the better of me,” he told Sky Sports. “Following on from last week I feel like it’s very close and to hit shots like that you get frustrated, but I shouldn’t have did what I did.
“It all bottled up and I had to let it go somehow and that’s what happened. I??don’t feel good about doing it but I will hopefully have a new three iron on the??way in the morning and be able to got out and play with another one.
“I wouldn’t encourage kids at home to do the same thing.??It felt good at the time but right now I regret it. I walked away with a bogey but was able to re-group and shoot a decent score.”
Describing the shot that led to him tossing his three-iron away, he added: “You can see I’m aiming left to try and cut it and it’s been frustrating this week because the shots I want to cut I draw, and the shots I want to draw I cut.
“I’m just not quite there with the swing the way I want to and another ball in the water wasn’t good.
“(I have) another couple of rounds just to try and find a little bit of??rhythm. I’m a little behind at the minute but it seems like the scores are quite??spread out so if I can get off to a decent start tomorrow you never know.”