Rory McIlroy, who was 7-over through eight holes, walked off the golf course at Honda Classic

Walking off the course before you're finished with a round is behavior we're used to seeing from a hot-head on tour. Or a guy that parks his van outside a Hooters during the Masters.

But not the No. 1 player in the world who's defending his title at a marquee event.

Rory McIlroy made for the parking lot at the Honda Classic on Friday morning after hitting a ball into the water on the 18th hole at the PGA National Champion course in Palm Gardens, Fla. McIlroy had started his round on the back nine and was already 7-over par after the first eight holes. He blamed his early exit on "severe wisdom tooth pain" that was affecting his concentration.

Here's the statement that McIlroy released after leaving:

"I sincerely apologize to the The Honda Classic and PGA Tour for my sudden withdrawal. I have been suffering with a sore wisdom tooth, which is due to come out in the near future. It began bothering me again last night, so I relieved it with Advil. It was very painful again this morning, and I was simply unable to concentrate. It was really bothering me and had begun to affect my playing partners. I came here with every intention of defending my Honda Classic title. Even though the results haven't revealed it, I really felt like I was rounding a corner. This is one of my favorite tournaments of the year and I regret having to make the decision to withdraw, but it was one I had to make."

McIlroy was having a tough couple of days before making a beeline for his car on Friday. He made a sloppy bogey on his 18th hole on Thursday to post an even-par round of 70. Then he was 7-over thru eight holes on Friday at the Honda Classic before getting to the same 18th hole that kept him out of red figures a day ago. McIlroy had already drenched two balls in the drink on the par-4 16th hole and was forced to make a 6-footer for triple-bogey after a double-bogey on the 11th.

Withdrawing from a golf tournament on the PGA Tour has lasting consequences. It means you're not eligible for the Vardon Trophy, awarded to the player with the lowest stroke average at the end of the season and something McIlroy won a season ago. McIlroy will not be repeating this feat in 2013.

This whole incident has shades of Tiger Woods at the 2011 Players Championship, when after just nine holes of his first round he left TPC Sawgrass. Back then Woods blamed his aching knee and Achilles for his early exit.

The AP's Doug Ferguson tweeted that Rory said, upon leaving PGA National, that he's "not mentally there." There will be much more to come of this, I'm sure, but for the third straight tournament of 2013, Rory McIlroy will not be around on Saturday and Sunday.

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