The American did not build on his early success, however, with four bogeys
including three in a row after his turn, at the first, second and third, to fall to one over par.
Sergio Garcia was as low as three-under but settled for a 70 after a bogeys
at the eighth and ninth to close his round.
Padraig Harrington remained two under for the tournament after one birdie and one bogey
in 12 holes but Luke Donald's hopes of becoming the first European to win a major since Paul Lawrie here in 1999 looked over after an outward half of 40.
I didn't make a bogey
today," he said after leaving the ball where it lay and heading back to the clubhouse.
Michelle Wie misses a putt on the 16th hole, starting a run of three straight bogeys
His frustration boiled over en route to a double bogey
six at the 12th.
Teesside's Vince Guest looked to be making a run at it after his first round 73 with a level-par front nine but the notorious back nine at West Lancashire took its toll when he dropped eight shots in four holes with bogeys
at 11 and 12, a double bogey
at 13 and a quadruple bogey
He chipped to about 10 feet but twoputted for his first bogey
of the day.
Morris slipped to a 74 yesterday and will rue a double-bogey
six at the 15th and bogey
four at the 17th while Mouland improved his opening-day effort with a 72 but a triple-bogey
seven at the 16th destroyed his hopes.
Gil Morgan, a three-time winner of the AT&T Classic being played this week at Valencia Country Club, led much of the opening round before a double bogey
on the par-4 eighth hole - his 17th - dropped him into a tie for fourth.
After his blazing opening round of 64 at Santo da Serra, he was steady rather than spectacular, with three birdies and a bogey
giving him a 70 for a 10-under-par halfway total of 134.
3 eagles, 82 birdies, 161 pars, 24 bogeys
, 1 double bogey
, 1 worse.