Louis Oosthuizen leads the pack heading into the final round of the Houston Open.

The South African carded another six-under 66 to leave him on 17-under for the tournament, two whacks better than Hunter Mahan.

Englishman Brian Davis and Carl Pettersson find themselves sharing third with a score of 14-under.

Davis could not replicate his magnificent 65, which had saw him provisionally share the second-round lead and shot a competitive 69 to keep him in the hunt.

Houston local Jeff Maggert had to finish his second round before the field began and managed to play himself into the halfway lead on 12-under.

However, he struggled to get his game going during his third round and dropped down the leaderboard, and now finds himself tied for 14th on eight-under.

Phil Mickelson went round in 70 again to improve his score to 11-under.