Zach Johnson shot a brilliant second-round 65 to share the lead at the Valero Texas Open, while Graeme McDowell is well poised to make a weekend push.

Johnson carded four successive birdies, and six and an eagle in total, in a seven-under-par round which matched Scotland's Martin Laird for the best of the day as he surged to nine under par for the tournament.

Teeing off on the 10th, Laird nailed five consecutive birdies after the turn and finished with another on the ninth.

That left him three shots off Johnson and fellow United States Ryder Cup player Ryan Moore at the top of the leaderboard, Moore carding five birdies in a blemish-free 67.

McDowell was a shot better on the first round, hitting back-to-back birdies on the 7th and 8th and finishing tied in 41st, one under for the tournament.

The only Irish representative at the event, Seamus Power, failed to make the after another disappointing round. Power signed for a 77, a shot worse that his opening round, and he finished eight shots off the cut-off point of +1.

First round leader Grayson Murray slipped into third after completing in 69 with bogeys on the seventh, 12th and 16th, and was tied with fellow American Andrew Landry (67) ahead of day three.

Ben Crane of the US shot a 66 to end the day in fifth alongside Laird and Canadian David Hearn, who managed a 37ft putt on the par-4 17th on his way to carding 68.

Sergio Garcia had a club-slinging meltdown on the 15th, hurling his driver into bushes during another troubled round.

Returning to the tournament for the first time in eight years and after a disappointing title defence at the Masters, the Spaniard looked likely to miss the cut after finishing with 72 - 11 shots off the lead.