The 24-year-old Texan would become the sixth, and the youngest, player to complete the Grand Slam if he were to win the PGA Championship. Graham DeLaet (68), Patrick Reed (69), Gary Woodland (69), Scott Brown (70) and Francesco Molinari (74) are at 211.
Day - US PGA victor in 2015 - started the day on six under putting him in the final group alongside Kisner and Matsuyama.
Day began the third round at 6 under, two strokes back of Kisner and Matsuyama.
Across the first 11 holes, Kisner had all pars except for a birdie on No. 7. He finds himself tied with Kisner for the lead. He nearly aced the 301-yard par-four 14th as well, his tee shot with a three-wood running over the hole before stopping eight feet beyond, from where he sank the eagle putt. "Hopefully, come Sunday, I can come back (as champion) and that would help increase the popularity of the men's game in Japan". I'll play tomorrow and assess my options for the rest of the year.
On Friday, Matsuyama shot a bogey-free 64 which had seven birdies, five of which came in the last seven holes.
Added Thomas, who made par on Saturday: "That tee shot, when you are not driving it well, it's not exactly the most comfortable shot in the world".
Kevin Kisner was efficient as ever with his wedges and putter in posting a 4-under 67 in the second round. He's the hardest worker out here right now just because he wants to win.
More importantly, he managed to keep the lead. It might seem like a lot the way Matsuyama and Kisner are playing, but it doesn't to Thomas. "But when I had the chances that I had and I just couldn't get the ball to go in on the greens, that is when I get the most frustrated I can get out there".
That took the world number 25 back to eight under and briefly level with Stroud before the latter bogeyed the 17th moments later and did the same on 18.
"It was a little bit of a safe shot into the green", he said. I did no scouting of that cup location.
"I told him I would like to see him play well here on out to show me something basically, and that doesn't sound right coming from a guy like me talking to Phil", Stricker said. "But I believe we can play anywhere and can win anywhere".
That steadiness was on full display on Friday.
"I kind of accept the fact that I'm essentially out of this tournament pending some form of insane stuff the next couple of days", Spieth said.
Like Matsuyama, Stroud is happy to be in the hunt.
"If I have a short putt, it's not a technical issue - I'm just not seeing the ball go in and staying committed", Mickelson said.
"I'm having a tough time visualizing the shot", he said.
"I don't know if the other players should be nervous or not, but this is my first experience leading a major, or tied for the lead after 36 holes [sic]", Matsuyama said.