Thomas finished the day T-4 at 5 under, two shots behind outright leader Kevin Kisner.
The first hole again proved a problem for the former Walker Cup player as he took five and another shot went at the short fourth hole. Then the storms arrived, and everything changed.
Despite his struggles, the 25-year-old played the hard final three holes better than his rivals, parring them all to finish the day much closer than he expected an hour previously.
Quail Hollow has big greens, but they "play small" because of how firm they are and large runoffs.
That could leave the final major of the year up for grabs over the final 36 holes on the weekend, but not for everybody. He said anyone who broke 70 was going great. Heavy rain and nearby lightning strikes forced players and spectators back inside, but the course yielded more birdies after play resumed. And now he's not sure what it will take.
Matsuyama is tied for second with Chris Stroud (71) as the duo chase Kevin Kisner (72). Olesen did the same with six birdies and two bogeys. To finally get a win is really magical. He loves Bermuda, the grass now in place at Quail Hollow, and his confidence soars when he's hitting it well.
"I haven't hit it this well this whole summer - a lot of average finishes", Kisner said.
"But I haven't been spot-on all week, and the worries I had about my swing showed up today in the way I played".
At stake in the year's final major tournament is the Wanamaker trophy and a top prize of $1.89m (1.59m euros).
He looked like the Day of old on Friday at Quail Hollow with his power off the tee and putting touch.
Matsuyama can get so locked in with his ball-striking that even his misses are great shots.
"I have replied to every single one of them", Stroud said the other day. In round one, it yielded 11 birdies and round two, just four, the fewest of any hole. Now, he wonders how much longer is season will last. Mickelson hasn't missed a team event since 1993. I think he's got the right game and confidence to make a run at this major. He made only one of them Friday.
Players making a move up included Rickie Fowler (two-under through 14) and An Beyong-hun (3-under through 15).
"On to the weekend to try and fire at stuff".