SAN ANTONIO — Matt Bettencourt looked more like the former PGA tour winner that he is Thursday than someone who's 183rd on this year's money list.
Peter Tomasulo looked like anything but a player fighting to keep his tour card.
Bettencourt and Tomasulo each shot 5-under par 67s Thursday to earn the surprising lead after the first round of the Texas Open, holding off a field that includes world No. 2 Rory McIlroy.
They took advantage of warmer and calmer afternoon conditions and held a one-stroke lead over a group of four players — including three-time major winner Padraig Harrington — at 4 under.
Harrington and Billy Horschel shared the lead following the morning tee times, battling chilly and windy conditions. They were joined by Bryce Molder and Harris English at 4 under in the afternoon.
McIlroy, who entered the tournament as a final opportunity to prep for next week's Masters, opened with an even-par 72 and is tied for 45th.
Playing in the final group of the day, Tomasulo posted the only bogey-free round. Taking advantage of a medical exemption following a rib injury two years ago, he closed with a 10-foot birdie putt on the par-5 18th.
Bettencourt made the tournament as an alternate after Henrik Stenson withdrew. The former Reno-Tahoe Open winner needed only 25 putts while playing after the temperature warmed considerably and the wind eased off in the afternoon.
The 37-year-old's two-year exemption on tour following his 2010 win in Reno ended after last season. He had bounced between the PGA and Web.com tours this season, making only one cut in five events.
Bettencourt played like anything but a journeyman on Thursday, crediting a recent medication change in helping to control his asthma and jitters that resulted from other inhalers. His lone bogey came on No. 4, and he took the lead from Harrington with a birdie on No. 17.
Bettencourt might have found his answer away from the course, but it was Harrington who felt right at home on the course in the early morning cold and wind — even if he didn't particularly enjoy the conditions.
The former British Open and PGA Championship winner from Ireland overcame the early morning chilly temperatures and steady wind to go as low as 5 under before finishing with a bogey on No. 18. He began his day with four layers of clothing in an attempt to stay warm as the Texas winds whipped in from the north.
McIlroy, meanwhile, continued the up-and-down play that has plagued him throughout the year and cost him the No. 1 ranking to surging Tiger Woods. McIlroy was 2 under early in his round, which began on No. 10 on the difficult 7.435-yard layout, but he found the water on the par-5 18th when his approach came up short.
That began a stretch of three straight bogeys, and he missed a 7-foot par putt on No. 9 to fall back to even.
While McIlroy struggled, Horschel continued to show the form that led to a second-place finish at last week's Houston Open. Horschel jumped from 60th to 24th on the money list following last week's performance, and he tied Harrington on Thursday with a final-hole birdie on No. 9.
Horschel had six birdies, including a stretch of four in five holes midway through the round, and he did so despite hitting only 7 of 14 fairways. He and Harrington had just 25 putts each, while McIlroy needed 31.
Ten players, including Jim Furyk, are two shots back of the lead at 3 under.