Vijay Singh shot a 7-under 63 to grab the lead after the opening round of the PGA's Greenbrier Classic. He leads Jeff Maggert, Jonathan Byrd and Martin Flores, by one shot. Tiger Woods stumbled to a 1-over-par 71 that included a double-bogey on the par-5 17th hole. Phil Mickelson also opened with a 71, eight shots behind first-day leader Vijay Singh.