Charley Hoffman carded a 5-under 67 on Thursday to take the early lead at the wind-whipped Texas Open.
Hoffman picked up his third PGA Tour win earlier this season in Mexico.
Aaron Baddeley posted a 4-under 68 and is alone in second place on the AT&T Oaks Course at TPC San Antonio. Max Homa is one stroke back at minus-3.
Phil Mickelson birdied his final two holes for a 2-under 70. He stands alongside Ryan Palmer in fourth place.
Texas natives Jordan Spieth and Jimmy Walker are among seven players tied for sixth at minus-1.
Matt Kuchar and Cameron Percy were the leaders after the morning wave finished in windy conditions. They carded even-par 72s and are now tied for 13th. The scoring average in the morning wave was 78.61, but improved to 74.86 in the afternoon.