Tour officials paired the three most recent major championship winners for the opening two rounds of the tournament and all three -- newly crowned U.S. Open champion Webb Simpson, Masters winner Bubba Watson and 2011 PGA Championship winner Keegan Bradley -- broke par Thursday. But it was Mathis who jumped in front thanks to a hole-in-one early in his round.
He started on the back nine of the TPC-River Highlands course, aced the par-3 11th with a 9-iron and played his first six holes in 6-under en route to his lowest score of the year.
Mathis is winless in his third full year on the tour and has only one Top 10 finish in his career, that coming in New Orleans this season.
Bradley wound up with a 68.
Jacobson, who challenged for the U.S. Open title in San Francisco last week before fading in the final round, had the lead Thursday before suffering a double-bogey at the par-3 16th.