Jason Kokrak, Roberto Castro and rookie James Hahn all fired a 9-under 63 on Thursday to share a one-stroke lead after the opening round of the Humana Challenge.
Russell Henley, Greg Chalmers, Doug LaBelle II and Aaron Baddeley are tied for fourth place at 8-under. The rookie Henley is coming off a three-shot win at the Sony Open in Hawaii.
"It was a perfect day," Henley said. "The weather is perfect. The greens were true. So, it's just trying to stay patient and let the birdies come to me."
Charley Hoffman, Jeff Maggert, Daniel Summerhays, Michael Bradley, Ricky Barnes, Cameron Tringale, Ryan Palmer, Jerry Kelly and Patrick Cantlay are tied for eighth place at 7-under, while 12 players, including Bo Van Pelt and Zach Johnson, are knotted at minus-6.
Phil Mickelson, making his PGA Tour season debut while dealing with flu-like symptoms, shot even-par. World No. 8 Brandt Snedeker fired a 5-under 67, 2012 Players champion Matt Kuchar carded a 2-under and 2012 U.S. Open champion Webb Simpson recorded a 73.
"I'm 95 percent better," said Mickelson. "I'm not contagious and the energy's coming back. I've been able to practice. I played a little bit yesterday and it's fine."
Defending champion Mark Wilson is tied for 153rd place after stumbling to a 5- over 77.
Three different courses are in play during the first 54 holes of this tournament -- the Palmer Private Course and the Nicklaus Private Course at PGA West, and La Quinta Country Club -- with the final round taking place at Palmer Private.
Kokrak played La Quinta on Thursday, Castro played Nicklaus Private and Hahn competed at Palmer Private.
Hahn, who earned his PGA Tour card by finishing fifth on the 2012 Web.com money list, tallied nine birdies during his bogey-free opening round. Still, the odds are against him, as only three players -- Jhonattan Vegas (2011), Arnold Palmer (1960) and Charley Hoffman (2007) -- have won the Humana Challenge in their first start at the event.
Kokrak and Castro should be able to relate to Hahn, considering both players are coming off of their rookie PGA Tour campaign. Kokrak missed the cut at the Humana Challenge last year, while Castro tied for 42nd place.
Thursday's 63 marked a career-low for Kokrak, who highlighted his round with a pair of eagles in a five-hole stretch. He turned the trick at the par-5 sixth, then did so again on No. 11 -- another par-5.
"I just tried to put it in the right spots, put it in the fairways," Kokrak said. "Out there, that's key. They're tighter fairways and if you can be in the fairway, you'll have a good opportunity for birdie."
Castro turned in a steady, bogey-free round to match his career-low from the final day of the 2012 Greenbrier Classic.
Henley opened his round with a trio of pars before carding an eagle at No. 4. He went on to birdie seven of his next 12 holes before stumbling to a bogey on the 17th. Still, he placed himself within striking distance of becoming the first rookie in PGA Tour history to win his first two starts.
NOTES: Hahn's only start on the PGA Tour prior to 2013 ended in a missed cut at the 2012 U.S. Open ... The best finish of Kokrak's rookie year was a Tie for second at the Frys.com Open ... Castro's lone top-10 finish in 2012 was a tie for seventh at the Greenbrier Classic.