Darren Clarke struggled to a five-over-par 77 in the final round of the Volvo Golf Champions tournament in Durban.
The Dungannon player carded a double-bogey at the 14th to go with five bogeys and two birdies as he finished on one over and in joint 24th place.
Padraig Harrington (67) was the best of the Irish on nine under, three shots behind winner Louis Oosthuizen.
Belfast's Michael Hoey (74) was back on four over with Simon Thornton (71) a further stroke back.
It was a disappointing finish to the event for former Open champion Clarke, who was just two shots off the pace after the opening round.
Three-times major winner Harrington was in title contention at one stage in the final round but ended in a tie for fifth.