Branden Grace holds a one-shot lead after the opening round of the Valero Texas Open, where Graeme McDowell also made a strong start.
The South African mixed seven birdies with a sole blemish to post a six-under 66 at TPC San Antonio, with Stewart Cink one of four players in a share of second.
McDowell and Brooks Koepka both sit in the group tied-fifth after opening-round 67s, while Ian Poulter is facing a battle to make the cut following a three-over 75.
Grace holed a 20-footer from the fringe to birdie the second but gave it back with a missed par-save from seven feet at the fourth, before three gains in a four-hole stretch saw him reach the turn in 33.
The world No 21 continued his birdie run with a close-range at the 10th and picked up further shots at the 13th and 14th to set a clubhouse target which wasn't matched.
Cink picked up four birdies in five holes after the turn on his way to five under, with Jon Huh posting a blemish-free card to also join Will MacKenzie one off the pace.
Steven Alker birdied his final three holes to make it a four-way tie for second, with McDowell one of 13 players on four under after a strong start to the week.
Soren Kjeldsen briefly threatened the lead with three consecutive gains from the fourth, only to three-putt the seventh and bogey the ninth to match Patrick Reed's opening 69.
Andrew "Beef" Johnston lies nine off the pace alongside Poulter, who needs to earn $30,624 in prize money this week to retain his full PGA Tour playing privileges.
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