Perhaps the 39-year-old now will after a battling display which seems to have added another string to his already well-bolstered bow. He's nearly certainly out of it heading into the final round on Sunday.
And then, Fowler took a second straight bogey at No. 12 to fall one shot behind Brooks Koepka. Thomas' 9-under 63 was one better than Johnny Miller's 63 in the 1973 final round at Oakmont.
Matsuyama, at number four the highest ranked player still in the field, starts at five-under along with young South Korean Kim Si-woo, amateur Cameron Champ, PGA Tour rookie Xander Schauffele and veteran Brandt Snedeker. Later, a long put for bogey rolled just right of the hole before he tapped in. He's back at 1 under as he finishes his round on the front nine.
In all, eight of the world's top 12 will the absent from the shootout for the title, including each of the top three for the first time since the world rankings were introduced in 1986. Day, however, said he felt ready to go before flaming out early.
It was a much different scene than Saturday, when Thomas matched a major record with a 63.
There are 68 players who made the cut at the U.S. Open, but a whopping 42 of them are under par.
The biggest surprise at this U.S. Open was not who was leading, but who was leaving.
He then bogied the 15 hole, hitting it short of the green in two and failing to get the up and down. Fowler will be among the later starters along with defending champion Dustin Johnson, who opened defence of his crown with shaky three-over 75 and will need to mount a charge to make the cut.
The soft, forgiving conditions created opportunity for major movement up the leaderboard for those players willing to take it.
It was McIlroy's first tournament since taking time off to tend to a recurring rib injury.
That's something Day, the No. 3 player in the world, rarely says at a major. He only shot 75, with just one birdie.
Koepka birdied No. 1 to move into a tie with Harman for the top spot.
Rickie Fowler was playing so cleanly at Erin Hills that the record appeared to be in jeopardy.
Now consider that the largest 36-hole comeback in U.S. Open history was 11 shots by Lou Graham in 1975. She thought for a second and replied, "16 birdies".
Spieth had a big grin on his face recounting the story.
Just like that, Casey is 4 over for the day and now five shots out of the lead.
Reed, who beat Rory McIlroy in the first singles contest at Hazeltine previous year and was wearing the pants from his Ryder Cup uniform, said: "You always can take that fire from Ryder Cup and use it in other events".
Johnson, who arrived late at Erin Hills following the birth of his second child on Monday, will now have extra time to spend with his infant son.
Brian Harman stood on the podium with hands on hips, giving answers in the kind of matter-of-fact voice expected from someone used to the spotlight of a major championship. But as the sun rose over Erin Hills, and the forecast was for no rain, Mickelson withdrew.
Rory McIlroy was left reflecting on a missed cut at the US Open for the second consecutive year on Friday after once again struggling to get to grips with the Erin Hills layout.
While Erin Hills was still not playing as hard as many past U.S. Open courses, it was beginning to firm up from the early week rain, plus the USGA had a few tricks up its sleeve.