Jason Dufner has a two-shot lead going into the third day of the Transistions Championship at Palm Harbor, Florida.
The American carded another round of 66 to leave him on 10-under-par.
Padraig Harrington, who had posted his lowest-ever round of 61 on day one, hit a two-over 73 to leave him on eight-under with America's William McGirt.
Luke Donald can return to the top of the world rankings with a win at the tournament this week.
The Englishman fired a round of 68 to end the day three behind the lead with five others.
