Matt Bettencourt and Peter Tomasulo both fired a 5-under 67 on Thursday to share the lead following the first round at the Valero Texas Open.
Bettencourt held the outright lead for the majority of the day, but Tomasulo birdied his final two holes with the last group of players at TPC San Antonio to join him atop the leaderboard.
Billy Horschel, Bryce Molder, Padraig Harrington and Harris English all sit in third place at 4-under, while 16-time PGA champion Jim Furyk is among 10 players tied for seventh at minus-3.
Rory McIlroy, who added this event to his schedule at the last minute to prepare for The Masters next week, carded an even-par 72 to sit in a tie for 45th.
Harrington and Horschel shared the clubhouse lead after playing among the earlier groups, but Bettencourt took the course and started to make his move with two birdies in his first three holes.
He gave away one of those strokes with a 2-putt bogey at the fourth, but quickly recovered with an 8-foot birdie putt at the fifth.
After parring the next six holes, he followed a 21-foot birdie putt at the 12th with an 8-foot birdie effort at the 13th to join Harrington and Horschel atop the leaderboard.
Bettencourt then took sole possession of first place with a 10-foot birdie putt at the 17th before closing with a par at the last.
"I'm just going to go out (Friday) and have fun. I haven't done anything great in golf in a couple years, so I just want to have fun and put the ball in play off the tee because it's a really fun golf course when you put it in play out here," said Bettencourt, whose last PGA win came at the 2010 Reno-Tahoe Open.
Tomasulo's bogey-free round opened with a par before he rolled in a short birdie putt at the second.
He then followed five straight pars with a 17-foot birdie putt at the eighth to hit the turn at 2-under.
A 9-foot birdie putt at the 11th moved him further up the leaderboard before he scrambled out of a greenside bunker at the 17th for a birdie and rolled in a 10-foot birdie putt at the last to grab a share of the lead.
Earlier in the day, Harrington had five birdies and 12 pars through his first 17 holes to hold the outright lead at 5-under, but stumbled to a 3-putt bogey at the 18th to fall into a tie with Horschel for the top spot.
"That was a pity. Takes the shine off the day. It wasn't a difficult putt," Harrington said about his second putt of the 18th hole, which came from just over four feet. "As I got over it I stood off it once because the wind was gusting from my left, which it shouldn't have been."
NOTES: Bettencourt was only added to the field after Henrik Stenson withdrew ... Harrington is seeking his first win since the 2008 PGA Championship ... Jeff Maggert, Andrew Svoboda and Sang-Moon Bae all withdrew during the first round. Bae was the only one to finish his round and carded an 11-over 83 before withdrawing ... Horschel has made 20 straight cuts ... Defending champion Ben Curtis carded a 2-over 74 in his first round.