It was a day for low scoring in Connecticut, as Schheffler and Eckroat each carded eight under 62s around the benign TPC River Highlands, enough for a two-stroke lead over the chasing pack headed by Rory McIlroy.
Scheffler rolled in five birdies on the front nine to make the turn in 30. He birdied the 12th, then hit his 3-iron all of 236 yards to give himself a ten-foot eagle putt on the par five 13th. Of course, he drained it.
"That 3-iron I hit in there was really nice," he told the press afterwards.
"It was pretty much exactly what I was trying to do. It was kind of one where I had to hit it really solid in order to get it there with the water short, and I just did pretty much exactly what I wanted to, and it felt nice."
Had Scheffler not bogeyed the 17th, we would have had the outright lead.
Meanwhile, with six birdies and an eagle, Eckroat was flawless for his 62.
"I wasn't fearing the left ball today, which is huge, and then whenever you're feeling comfortable with other things, other things start to fall in line," said the American.
"Felt great over the putter, and just a really solid day, and I felt confident, which it was nice to feel that this season. It's been a while."
McIlroy had a bogey-free 64 and is tied with Ryder Cup captain Keegan Bradley and Wyndham Clark on six under.