LAS VEGAS — Webb Simpson maintained a four-stroke lead Saturday in the Shriners Hospitals for Children Open, birdieing four of the last seven holes at TPC Summerlin Making his first start since helping the U.S. win the Presidents Cup, the 2012 U.S. Open champion shot a 4-under 67 to reach 19 under. He opened with rounds of 64 and 63. "The conditions were perfect," Simpson said.