Sabbatini entered the final round with a five-stroke cushion. Yang, however, made a hard charge on the back nine, whittling Sabbatini's advantage to just one shot through 15 holes.
But the South African went on to claim his sixth career PGA title by birdying No. 16 and then hanging on to finish at 9-under-par 271, one shot better than Yang (4-under 66).
Jerry Kelly grabbed sole possession of third place, registering a 67 to end at 7-under 273.
Fourth place went to Ricky Barnes (67) at minus-four.