Yuan, chasing a first tour title, started the season's first full-field event at Waialae Country Club in Honolulu, Hawaii, as a full member of the tour - inheriting the last spot when Spain's Jon Rahm jumped to LIV Golf and was suspended, losing his place in the FedEx Cup standings.
Yuan admitted it was "kind of a relief" to have the security of full membership, which gives him guaranteed access to more events, but said it won't change his early-season aims.
"Before I learn the news I was really trying to get myself ready and come out and play good in Hawaii and on the West Coast and try to earn myself back on tour," said Yuan, who was able to skip a return to Q-school.
"Luckily I got full status, but I'm still trying to do the same thing and come out here and play the best I can."
On Friday that meant a steady climb up the leaderboard that saw him first in the clubhouse on nine-under par 131 after a two-putt birdie at the par-five 18th.
He was joined by Eckroat, who had five birdies and one bogey in his four-under 66, which was capped by a birdie at his last hole - the par-five ninth.
An played without a bogey, making the last of his six birdies at the 18th to conclude his 64.
"Didn't get as many putts as I would like to fall, but easy to look back and say that," said Eckroat, who was celebrating his 25th birthday. "Really solid round. Shooting 66 isn't a bad birthday."
Sixteen players were within two strokes of the leading trio, starting with a group of 10 players on 132 that included first-round leader Cam Davis of Australia, veteran Stewart Cink and Chris Kirk, winner of the season-opening Sentry tournament at Kapalua on Sunday.
Another six players were tied on 133.
Woodland coming back
Yuan had two top-10 finishes last season, and said he would draw on those experiences in what promises to be a hard-fought weekend.
"I had a couple chances last year being in the final two groups, having a shot on the weekend," Yuan said. "I feel like I just got to do what I did last two days: be patient and stay committed, know exactly what I'm going to do before I hit a shot and see how it turns out."
Those missing the cut included former US Open champion Gary Woodland, who was playing for the first time since September surgery to remove a brain lesion that caused anxiety and fears of death.
"There was a time where I didn't know if this was going to be possible," an emotional Woodland said after shooting a second straight one-over par 71. "It was a good week for me from a mental standpoint.
"I needed to be mentally sharp to get where I want to be in the world. It's coming back."
