And it will be there over the next two rounds.
PONTE VEDRA BEACH, Fla. His previous lowest was a 67 during the third round of the Valspar Championship.
World number three Jon Rahm, of Spain, is a further stroke adrift of Day after a 70.
Either way, fans at the Stadium Course were ecstatic to see Woods capitalize.
"I mean to be eight-under there through 12, realistically I probably could have got a couple more out of it and got to 10 for the day", said Woods. Feel like I'm putting well.
"When you're out there competing in a big tournament, you're as focused as can be, but then at a certain point, maybe on 13 today, you start just - like a kid, just kind of laughing", he said.
Spieth did his damage on the back nine, playing it in 31 strokes, including birdies at the final three holes.
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A Japanese newspaper on Friday raised the possibility of Chinese President Xi Jinping also travelling to Singapore on June 12 . Mr Will Saetren, research associate at the Institute for China-America Studies, said: "The DMZ already had a historic summit".
So Woods has some work to do to stick around Sunday.
"That's golf, unfortunately", Woods said.
And Woods is not stopping there, as he hopes to continue to rebuilding his game: "Eventually, I want to put all of the pieces together".
"Unfortunately, the part of the ball that was showing was just all the white and dimples", said Fowler. During the second round, he failed to get any of seven shots from the same distance within 15 feet. He ended up making par each time.
But he made his first mistake at 14 when he caught an very bad lie from a wild tee shot and an underwhelming chip resulted in a two-putt bogey. All in all, with a five-shot lead, I think it was a good, solid day, but I'd like to clean up those mistakes and come out tomorrow with an even sharper round.
Woods has struggled of late.
Spieth was 5 under on his round through 11 holes and wondered if he had the low round of the day. Woods hit a patented squeeze-cut stinger that found the center of the fairway then hit a wedge approach that looked like it might find the water left of the green.
Those miscues were huge for Woods.
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Meanwhile, the annual inflation rate in the US edged up to 2.5 percent in April from 2.4 in March, matching market expectations. Turkey engaged in intense diplomacy and managed to convince Tehran to sit around the table to reach a nuclear agreement.
After he pulled a 288-yard drive left into the water, on the par-4 seventh, McIlroy chipped his fourth shot to 4 feet to limit the damage, and rolled in the bogey putt to move him to 1-over for the round.
McIlroy doomed his weekend at the famed par-3 17th.
He just hasn't shown any signs of cracking.
Simpson, the 2012 US Open champion, had started the tournament by compiling an accomplished 66 but accelerated clear of the field with a stunning spurt on the back nine on Friday.
It was the first of successive double bogeys for the 2015 champion, who finished on one over par.
Although that form slowed later in the round, Woods had few complaints and enjoyed playing some of his most impressive golf in recent years after starting well. That's what led him to hire Justin Parson. "I just tried to play it cool and not sound like a total dork". But 17 is a hard hole to get through. I've hit quality irons before and I was able to convert today and got rolling early. So might have caught a gust.
Having dropped to world No.71 without a win in two years and a top 10 result in nearly 12 months, Scott faces a month-long battle to qualify for the US Open. His confidence is as high as ever. "I can't recall so many people here so early on Saturday morning". "I wasn't quite as sharp as I'd like to be, dropped a couple shots".
Manchester United secure second place with West Ham draw
The three at the back system was used to counter the similar formation used by West Ham who rely heavily on width to get forward. It was competitive", said Mourinho. "I don't think they [United's players] grasp the importance of these games".
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