"Everything is going in". You feel like no matter what, you're going to make it.
"But just a fun day". "I felt like everything was working today".
On the back nine, Simpson went off and made six straight birdies from holes 11 through 16.
He ended up with the first of back-to-back double-bogeys, his one-under round of 71 giving the 2015 victor of the tournament a one-over total that saw him miss the cut by two shots.
"It wasn't a mistake", Simpson said.
"I was in between clubs", he explained.
Simpson's fellow first-round leader, American world number one Dustin Johnson, is now eight shots back after a 71, one behind the world's seventh-ranked player, Jason Day of Australia (67).
Webb Simpson has thrown a hand grenade into this Players Championship, and everything is now set up for a fascinating moving day.
However, with a five-shot lead Simpson does surpass Day (four strokes) for the largest 36-hole lead in Players history.
'Never in a million years did I think someone would have a chance to shoot 61 around here, ' said an incredulous Sir Nick Faldo, on American television.More news: Israel hits 'Iranian' targets in Syria in response to attack
A birdie on 16 looked to have been enough for McIlroy to make the cut - but a double-bogey on the infamous 17th brought a premature end to his week in Florida.
"I think I started tidying up a few of the areas I had (trouble with) last (week) and I think the swing is coming along".
In addition to Couples, Greg Norman (1994), Roberto Castro (2013), Martin Kaymer (2014), Day (2016) and Colt Knost (2016) have shot 63 on the Stadium Course. Simpson will play with Charl Schwartzel in the final pairing in Round 3.
As Rory McIlroy missed the cut for the PGA Tour's $11m flagship event first time since 2012, Shane Lowry dramatically scraped in for the weekend alongside Tiger Woods, Justin Thomas and Jordan Spieth thanks to a miraculous closing par.
High-profile casualties on day two included Rickie Fowler, Hideki Matsuyama and Phil Mickelson. He was inside the cut line until hitting into the water on the 17th and making double bogey.
All of that made what Simpson was doing that much more impressive.
"It was just awesome", said Spieth, who played with McIlroy and Thomas. "We have to figure out a way to put it together, and I have not done that consistently this year so far". We were hoping for it.
"I have to be a little defensive not because of the lead but because of what is out in front of us tomorrow", he said. But 17 is a hard hole to get through.
Simpson's struggles at the 17th boiled down to being unsure of about hitting a pitching wedge or sand wedge from 140 yards. His chip came up short, and he missed an 18-footer from the fringe for par. "It was unfortunate, to be honest". If I can shoot 9-under today, a guy can go out and shoot 7-, 8- or 9-under [Saturday] and shrink it pretty quickly. "I didn't get off to the start I wanted to".