Former world No.1 Rory McIlroy surged into contention for his first win of the year in the Players Championship, despite squandering a wonderful chance to create tournament history.
McIlroy carded seven birdies and an eagle in his first 16 holes at Sawgrass and came to the par-five ninth, his final hole, needing a birdie to set a new course record of 62.
However, faced with a second shot from 271 yards, the four-time major winner surprisingly opted to lay up and then missed the green from 90 yards with his approach, before fluffing a chip and running up his only bogey of the day.
The resulting 64 left McIlroy on eight under par and two shots behind clubhouse leaders Jonas Blixt and Alex Cejka, who had both recorded their second successive rounds of 67.
American Colt Knost was a shot behind after earlier also missing out on the course record, the world number 184 shooting 63 after three-putting the 18th from 40 feet.
"I've got it in my head with the ninth hole that any time that I have gone for the green it has not really worked out for me," McIlroy told Sky Sports. "I had a good number today and laid up with a nine iron.
"I probably had two iron to the front of the green. In hindsight, with that pin being on the left side, anywhere on the right I probably had a chance to get up and down. I thought get it within 100 yards and take my chances from there and just didn't hit a great third shot and left myself in a difficult position."
McIlroy felt he had got the worst of the weather as one of the later starters on Thursday and was pleased to take advantage of the better conditions on Friday morning.
"It was benign, soft greens and the back nine you could not get it any easier, so to take advantage of that was really nice," added McIlroy, who is now a combined 44 under par for the back nine and 12 over for the front since 2013.
"I was going well and it would have been nice to make a four on the last, but 64 is still a great score and hopefully I'm not going to be too far behind going into the weekend. I hit a lot of quality shots today. I feel like my game has been under control the last four rounds so hopefully I can continue like that over the weekend."
Knost, who carded 10 birdies in 15 holes from the third, admitted nerves had contributed to missing his par putt on the 18th from four feet, adding on PGA Tour Live: "I hit a pretty good putt to be honest and it just lipped out on me.
"It was cool to be in the mix and knowing I could do something that no-one else has done but we have two more days to do that."
The spectacular scoring continued as American Will Wilcox made the first hole-in-one on the 17th since 2002 and Shane Lowry bounced back from a poor start with the sixth eagle in tournament history on the 18th.
Lowry, who was two off the lead after an opening 65, had bogeyed the 14th and birdied the 16th before dumping his tee shot into the water on the 17th, but then holed out from 120 yards on the last to get back to eight under par.
That was three shots behind world number one Day, who had birdied the second and fourth to get back in front on 11 under par, with Cameron Tringale joining Blixt and Cejka on 10 under thanks to four birdies and one bogey in his first 10 holes.
Day extended his lead to two shots with a birdie on the seventh and had just saved par from a bunker on the eighth when an approaching storm forced play to be suspended.
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