NAPLES, December 14, 2013 (AFP) - Kuchar and English are at 20-under-par 124 through 36 holes on Tiburon Golf Club's course.
Retief Goosen and Freddie Jacobson shot a 61 to grab second place at 16-under.
Ian Poulter and Lee Westwood also posted a 61 to share third place. Poulter and Westwood are level with Charles Howell and Justin Leonard (67) at minus-13.
Overnight co-leaders and defending champions Kenny Perry and Sean O'Hair shot 69 and dropped into a tie for sixth with Rory Sabbatini and Scott Verplank (64) at 11-under. Perry and O'Hair hurt their chances with a double bogey at the ninth hole.
Kuchar and English found themselves tied for the top spot after Friday's modified alternate shot format and they built on that success during Saturday's better ball.