article_snippet: The 36-year-old San Antonio resident, a one-shot leader at the halfway stage, is nine under ahead of Sunday's final round - four shots clear of Jordan SpiethJordan Spieth.
article_snippet: Billy Horschel is third on three under par, a shot clear of a five-strong group including Zach Johnson and Brendan Steele.
article_snippet: Kevin Na and Chris Kirk complete an all-American top-10, with Australian Aaron Baddeley the highest placed non-American alongside Kevin Na and Chris Kirk on one under par.
article_snippet: Spieth carded six birdies, three bogeys and a double bogey to lie second, while Horshel helped Horshel to third by birdieing the final three holes.
article_snippet: Five-time major winner Phil Mickelson, meanwhile, was even par after a 74 which featured an eagle, a birdie, three bogeys and a double bogey.
article_snippet: World number six Spieth, like third-placed Horshel, was one under for the day but was not overly impressed with some aspects of his third round in San Antonio. '
highlights_snippet: The 36-year-old is on nine under par, four shots ahead of Jordan Spieth .
  
highlights_snippet: Five-time major champion Phil Mickelson is on level par .