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Padraig Harrington has lost track of how many times he has set the course record. Most of them were when he was just starting out his career, young enough to see opportunity instead of the risk of failure.

"When I was a young pro and naive and innocent, I used to go out there and shoot more course records than now as a seasoned pro with a lot of fear and damage in my system," he said Thursday after opening with a 61 to establish the record at Innisbrook.

He began his week at the Transitions Championship with a hole-in-one during the pro-am, using a 6-iron on the fourth hole. Harrington tried to count up the number of aces he has made in his career and was off. Way off.

He thought he had as many as 12. There have been only six.

"And the fact that I can remember the clubs and the shots and everything about them suggests that there really isn't a seventh," Harrington said. "I just assumed I had more. So don't believe whatever a professional golfer says."

The only thing that can be trusted is the score on the card.

And it was unbelievable.

Harrington opened with two birdies and closed with three straight birdies along the "Snake Pit" stretch of holes on the Copperhead Course at Innisbrook. That included a 75-foot birdie putt from one end of the 17th green to the other.

How good was his 10-under 61?

It was one shot better than the previous record set by Mark Calcavecchia in 2007 and Jeff Sluman in 2004.

It was three shots better than anyone else in the opening round on a gorgeous spring day. Will Claxton had a 64. Claxton played with William McGirt, who shot a 66. Harrington nearly beat their better-ball score.

Perhaps most impressive is that Harrington was nearly 8.7 shots better than the course average. And he managed this 61 despite failing to birdie three of the par 5s at Innisbrook. That included a simple, uphill 6-foot putt on the 11th hole in which he "choked like a dog." And it was probably a good thing.

It was the one time Harrington started thinking ahead, wondering if this day was so good that a 59 was in the works.

"I got over it and started thinking, 'If I hole this, I'm 7-under par, seven holes to go, I only need to make five more birdies,'" he said. "I just got totally out of where I should have been, hit a bad putt and missed. But if anything, it kind of got the 59 out of my head. So as much as I did choke, it made it easier for the rest of the holes."

The 61 was the lowest score of his career in an official event. His previous best was a 62 done three times, most recently at the 2009 Portugal Masters. He also had a 61 at the Nedbank Challenge in 2001, though it was an unofficial event and didn't even count as a course record because of preferred lies.

Luke Donald, at No. 2 the highest-ranked player at Innisbrook, opened with a 67, which he described on Twitter as a "solid start."

He was six shots behind.

"Never easy when you walk on the 1st tee and you're already 10 back!! Some round by Paddy," he tweeted.

Kenny Perry, the 51-year-old making a rare appearance against the kids, was in the group with McGirt and Jim Furyk at 66. Justin Rose, coming off a win at Doral last week, was at 67. Defending champion Gary Woodland opened with a 68.

It was only a start for Harrington, but an important one for a three-time major champion who has gone 38 tournaments over the last 17 months without winning. Harrington says he's actually playing better now than when he won the Johor Open, but such is golf.

"I play better on the Monday, Tuesday, Wednesday than I do on the Thursday, Friday, Saturday, Sunday," Harrington said. "I'm trying to stay patient. I know my game is good. One of the hardest things is to wait with confidence. I'm feeling like things are ready to happen. Obviously, today it showed the potential. Today is a peak. But we'll wait and see what happens over the next number of weeks."

Did anyone see a 61 at Innisbrook?

"I did. I watched it," said Geoff Ogilvy, who played alongside Harrington. "On the first tee, I didn't see 61. But after you see it done ... the only really, completely unreasonable birdie was on the 17th. There was never any stress."

That birdie putt on the 17th was from 75 feet, and Harrington said it looked good for the last 15 feet.

But if there was one putt that reminded him how everything was falling his way, it was the 6-foot birdie on the 16th, atop a crown in such a way that Harrington wasn't sure which way it was going to break. He guessed right.

"You're really guessing at which way it's going to go, but on your day, it goes the right way," he said. "I guarantee you there will be a lot of players having a frustrating day, telling you they hit it exactly where they wanted and it missed."

With a wedge into 15 feet on the last hole, he had no doubt.

"When it's your day, I could have turned my back on the hole and I would have holed the putt on the last," Harrington said. "That's just the way it is when things are going for you."