Louis Oosthuizen took the tournament lead in Round 2, and it's clear that he has no interest in giving it away. Through his first nine holes in Sunday's Round 4, Oosthuizen has played nearly mistake-free golf, and it's been enough to preserve a four-stroke lead.
The South African responded to an eighth-hole bogey by managing an impressive eagle on the ninth. His partner and closest competitor, Paul Casey, birdied the same hole. Casey stands in second, four shots behind Oosthuizen, and Martin Kaymer and Lee Westwood. hold possession of third.
Down the leaderboard, Alvaro Quiros, who has had a relatively quiet tournament, finished strongly with a 5-under final round that, at least for the moment, has him in the top ten. Mark Calcavecchia, who was near the very top at the end of Round 2, has fallen apart in post-cut play, having followed up his 77 score in Round 3 with an 80 on Sunday. John Daly ended up with a respectable finish at 1-over for the tournament.
Tiger Woods shot even for the day to preserve a 3-under score for the tournament, which at the moment is good for a tie for 24th. Phil Mickelson, meanwhile, stumbled to a 3-over final round to fall 22 spots down the leaderboard.
Here is how the top of the leaderboard looks, with all the golfers now in the back nine:
1. Louis Oosthuizen (-16)
2. Paul Casey (-12)
T3. Lee Westwood (-8)
T3. Martin Kaymer
T3. Henrik Stenson
6. Rory McIlroy (-7)
T7. Robert Karlsson (-6)
T7. Retief Goosen
T7. Dustin Johnson