Straka shoots 63 to lead Safeway Open

Straka was flawless in his first start on Thursday, the unheralded Austrian golfer carding a nine-under-par 63 in Napa, California.

The 25-year-old holed nine birdies, hit nine of 14 fairways and 15 of 18 greens in regulation to top the leaderboard at the Silverado Country Club.

Chase Wright posted a 64 to be a shot off the pace, with American star Phil Mickelson lurking at seven under.

Mickelson was part of the United States' Ryder Cup defeat to Team Europe in Paris but the veteran returned to the golf course and registered a 65 to be third, which included a run of six successive birdies.

"I was surprised at some of the shots I hit. I honestly have been hitting it just terrible, and today was just an anomaly," Mickelson said. "Don't let the good round fool you; I'm not at my best. But today, a few things clicked and it was fun."

Brandt Snedeker's 66 saw him in an eight-way tie for fourth position at the PGA Tour tournament.