Harrington has not won a sanctioned tournament since last year at the PGA Championship, when he became the first European in history to win successive majors in the same season.
The Irishman was about the only one not terribly excited.
Theres no relevance at all, he said. Its just a round of golf.
It was a good one, though, and it gave him a two-shot lead over Scott Verplank, Tim Clark and Prayad Marksaeng of Thailand.
Tiger Woods kept alive his streak of breaking par in the opening round for the 11th straight time at Firestone, where he is going for his seventh victory on the tree-lined course. He didnt do anything special in his round of 68, although it kept him in the picture.
Phil Mickelson got off to a rough start in his return to the PGA Tour. He played bogey-free on his back nine and picked up three birdies to salvage a round of even-par 70.
Harrington spent most of the year working tirelessly on his swing, always looking to improve, never overly concerned when it didnt come together as quickly as he might have wanted. He missed five straight cuts at one point, and hasnt finished in the top 10 since he opened his season at the Abu Dhabi Championship.
On a soft and serene afternoon ' and a week before his title defense in the final major of the year ' this was a good step.
Harrington said thats all it was.
It doesnt change the last six months, it wont change the next six months, Harrington said. Its only a game of golf, one particular round. I wouldnt put too much significant into it because what if I went out there and shot 76? Would I let it affect tomorrow? I think I would not put much emphasis on the fact that I shot 64. Im comfortable with it.
For all his birdies, it was a par that got him going.
Harrington watched a marginal shot take a wicked bounce to the left of the 13th green, his fourth hole of the round, leaving him a tough chip with not much green between him and the flag. He hit it to 5 feet and made the putt.
Those were the pars he wasnt saving all year, and it seemed to free him up for the rest of the day. He surged into a share of the lead with a 12-foot birdie on No. 1 and a two-putt birdie on the par-5 second, then picked up bonus birdies from about 25 feet on the seventh and eighth holes, the latter from just short of the green.
Not since his 66-66 weekend at Oakland Hills last year at the PGA has he made the most out of a round, and those last two birdies certainly brightened his mood.
I walked off the golf course feeling like I got a couple more shots, Harrington said. And I feel good about the fact that I got one or two more. If I shot 66, I would have said, Well, thats about right. Sixty-four is a little bonus.
In such tame conditions, 40 players were at par or better.
Woods has never opened with worse than a 68 since he first came to Firestone in 1997, and while he wasnt particularly crisp, he came through with birdies on the 12th and 13th holes to alleviate any stress in his start. A week ago, he was tied for 95th after the opening round before winning the Buick Open.
There are only 80 players at this World Golf Championship ' and no cut ' which helps.
I hit it good on the front nine in stretches, Woods said. Starting out, I hit a couple of bad shots there and in the middle part of the round I got it back. A little scratchy coming in, so it was kind of in spurts today.
British Open champion Stewart Cink, playing 18 holes for the first time since his playoff win over Tom Watson at Turnberry, bogeyed two of his last three holes for a 69. His only disappointment? He wasnt introduced as the British Open champion.
Mickelson has been more focused on his family. His wife and mother are battling breast cancer, although they are progressing enough that he could return to golf. Two holes into his round, he missed on a flop shot and a 3-foot putt and took double bogey, and Lefty went out in 38. He turned it around, however, and hopes hes not far off.
I think when you get in competition, I wasnt trusting myself as much, Mickelson said. The pins start to get tucked, and you cant miss it in certain spots, and I start kind of steering it a little bit. The last eight holes, I made a few better swings.