Derksen, who also led by two strokes after the second round, had a 54-hole total of 6-under 210 on the Pinx Golf Club course.
It was very tough ' I think it was unfair and unplayable, Derksen said. I think there was definitely a lot of luck involved today.
The only thing you can do is to just do your best. I did that on every shot I played today, and Im still two in front. So I guess thats the best part of the day.
The leading 10 players all shot over-par rounds Saturday and only one of 74 players in the field for the weekend broke par ' Francois Delamontagne of France with a 71.
It just was a very solid, long game, and I had a good putting on the short one, so thats the secret to making the putts in these conditions, Delamontagne said. Im from Brittany in France, and theres a lot of wind as well.
Spains Pablo Martin (74) was in second at 4-under 212, followed by three players tied for third, four off the lead ' South Koreans Kang Wook-soon (77) and Kang Kyung-nam (75) and Thongchai Jaidee (77) of Thailand.
Ernie Els was in a five-way tie for sixth after a 73, five shots back of Derksen.
Englands Lee Westwood shot 76 and was 10 strokes back, while American Fred Couples shot 81 and was at 10-over 226.
Play was suspended for three hours in the morning due to heavy fog.
When it resumed, Derksen birdied the fifth hole, but dropped shots on the sixth and ninth before making an eagle on the 10th.