In his latest round, Hoffman hit a 126-yard approach shot within 3-feet of the pin to help him birdie 18 and separate himself by a stroke from Hunter Mahan, who posted an early 62. Bubba Watson was two strokes back.
Hoffman said he thought he might have a chance to go even lower, and was flirting with 59 after making eagle on 10 and 12, and getting to 8-under par with a birdie on 16. His 28 on the back nine was the lowest 9-hole score on Tour this year
''I knew I had some chances coming in,'' he said. ''But when it's said and done, as I displayed last year, 16, 17 and 18 aren't an easy test. So I was just trying to make some pars coming in.''
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Hoffman, Mahan and Watson all have interesting histories in Connecticut.
Hoffman finished tied with Watson for second last year after it seemed he had the tournament sewed up. He made double bogey on 17, then bogeyed the 18th after failing to get up and down from a greenside bunker, handing Marc Leishman the title.
''It's nice to come back after that finish last year, and come back and shoot 61 and put myself back in the lead,'' Hoffman said.
Mahan is the 2007 champion and has two second-place finishes in his 11 previous starts at the TPC River Highlands.
''I think this is the most comfortable course on Tour for me,'' he said.
Coming off a fourth-place finish after being in the final pair at the U.S. Open, Mahan kept it rolling here, opening the day by making the first of eight birdies during a bogey-free round. He was also at 8-under with three holes to play before shooting par on the final three holes.
''This is a golf course where you can be aggressive off the tee if you want to be, but you can also play it safe,'' he said. ''I choose to be mostly aggressive, and it gives me some short irons. I'm happy to take on pins with my short irons. So it's a combo of things, but all I know is when I step on that tee, I feel like I can hit any shot out here.''
Watson finds himself in contention again after winning in 2010 and tying Hoffman as the runner up a year ago. He said there is a reason so many familiar names are at the top of the leaderboard.
''These are guys that love this course, that love this tournament, they love Travelers and how they've treated us here,'' he said. ''And so, you're always going to see pretty much some of the same guys up there because they enjoy this area and this golf course.''
A group of six golfers was four strokes back.
The biggest ovation of the day came when Justin Rose was introduced on the first tee as the U.S. Open champion. Rose went on to shoot a 67, leaving him in good shape heading into Friday.
''Obviously, I'm playing well,'' he said. ''I just knew I had to get through today without too much damage. If you manage to keep it in the mid-60s for most of the week, you should do pretty well.''
Rose also announced that he is changing management companies, leaving British-based 4Sports & Entertainment for Excel Sports, the same company that represents Tiger Woods.
''I just felt with me playing so much here in the States and where I felt my game was going, I just felt it was a decision I wanted to make,'' he said.
The round marked the pro debut Chris Williams, the top-ranked amateur in the world the past season. He shot a 1-over 71, with two bogies and a single birdie.
''The first tee, I was a little nervous,'' he said. ''But then it was the same old, same old. I didn't play very well, so that was pretty frustrating, but I got it out of the way.''