Phil Mickelson's rivals at the BellSouth Classic will start today's final round knowing that, barring spectacular collapse, the best they can hope for is second place.

Defending champion Mickelson tightened his left-handed grip on the title with a five-under-par 67 in the third round to open up an eight-stroke lead.

Americans Zach Johnson and Jonathan Byrd share second place at 13-under-par 203.

Despite missing a three-footer for par on 16 and running up a double-bogey seven at the last after twice finding water, Mickelson picked up three shots on the back nine to close in on his 28th PGA Tour title.

The American left-hander matched the tournament's 54-hole record of 21-under 195, set by compatriot Larry Nelson in 1988 when the event was played at Atlanta Country Club.

David Howell's 70 took him into a tie for ninth on seven under, while Padraig Harrington is one stroke further back and joint 15th following a 71.