Rory McIlroy finished the third round of the Valero Texas Open four shots off the lead as he sought a morale-boosting victory ahead of the Masters.

The world number two shot a one-under-par 71 in San Antonio as American Billy Horschel retained his two-shot overnight lead.

The Northern Irishman was six under for the tournament going into the final round and in a tie for fourth place.

McIlroy, a late entry for the tournament as he searched for form leading into Augusta, shot a magnificent 67 yesterday and started in similar vein today with two birdies in his first three holes.

Things looked to be going wrong with bogey fives at the fourth, 10th and 11th before birdies at the 12th and 14th moved him back into contention.

Horschel opened with back-to-back 68s and a 70 today, featuring five birdies and three bogeys, put him on 10 under, two clear of compatriots Charley Hoffman and Jim Furyk.

Hoffman also went round in 70 with five birdies and three bogeys, while Furyk birdied the last, his fifth of the round too, to shoot a 69.

McIlroy was in a group of three on six under with Ryan Palmer, who had the best round of the day, a 68, and Bob Estes, who shot a 69.

Palmer had four birdies in a flawless round, while Estes looked set to match him only for a bogey at the second last to peg him back.

Three-time major winner Padraig Harrington, whose last tournament win came on the Asian Tour in October 2010, was with Scotland's Martin Laird in a group of five on five under.

Jeff Overton, KJ Choi and Daniel Summerhays completed the quintet.

Harrington and Laird both shot 70s today, the Republic of Ireland player with five birdies and two bogeys, including a dropped shot at the last.

Laird had an eagle at the par-four fifth but also had three birdies and three bogeys

David Lynn was the highest-placed Englishman in the field on three under overall after a third-round 71.

Shane Lowry is on two under after shooting a 72. 

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