Published: Dec 03, 2011 4:56 PM EST
Updated: Dec 04, 2011 7:30 AM EST

SUN CITY, South Africa (AP) - Lee Westwood shot 10-under 62 to grab a seven-shot lead at the Nedbank Golf Challenge on Saturday and take a big step toward retaining his title.

The No. 3-ranked Westwood produced the best round ever under normal rules at Sun City as he reeled off 10 birdies to power to a 16-under total of 200 and take control of the $5 million invitational event with one round to play.

After Padraig Harrington's 61 in 2001 - when players were allowed to clean and place their ball because of wet weather - Westwood's performance was the lowest score in the 30 years of the Nedbank Challenge.

The Englishman picked up eight shots on overnight leader Graeme McDowell (70), who shared second on 9 under with Robert Karlsson (69).

Westwood didn't drop a shot in a third-round performance even more commanding than the second-round 64 he shot here last year to set up an eight-stroke win.

He left the world's top-ranked player, the No. 4-ranked player, two current major champions and one former major winner all trailing in his wake.

The Nedbank defending champion's birdies came in clutches as he grabbed three in a row from No. 2 and three more in succession through the turn. He finished by picking up four more shots on Nos. 14 through 17.

Westwood made birdie on each of the four par-5s and his score would have been even lower had he holed one of the four eagle putts he had on those long holes.

"If you ask me now (about) the poor shots I hit in the round, I probably could not tell you one," Westwood said. "I hit it over the flag or right where I was aiming all day. It was as good as I've played in a long time."

McDowell - the 2010 U.S. Open winner - had an eagle, three birdies, a bogey and a double-bogey to share second with Karlsson, who carded his third straight 69 at Gary Player Country Club.

American Jason Dufner returned a 2-under 70 after dropping a shot on No. 18. The Nedbank Challenge rookie was tied for fourth with No. 4-ranked Martin Kaymer, who also shot 70 with five birdies, a bogey and a double-bogey.

But none of the 12-man field - which also features top-ranked Luke Donald, Masters champion Charl Schwartzel and British Open winner Darren Clarke - could come close to the consistent brilliance of Westwood.

"It is great that it is a strong field this week, but you do not go in thinking about that at the start of the week," he said. "I enjoy playing this golf course. It is one of my favorites and you get what you deserve.

"It all went to plan."

Donald was unable to launch a challenge as he was pulled back by bogeys early and late in his round to go with four birdies. The world's top player shot 70 for a 5-under total of 211 for eighth place, 11 shots off the pace.

South Korea's Kyung-tae Kim and South African Schwartzel shared sixth at 6 under, a shot ahead of Donald.

Behind Donald, England's Simon Dyson (75) was ninth on 1 under, Denmark's Anders Hansen (77) 10th on 2 over and Clarke struggled to 76 - after a 69 on Friday - to drop to 3 over.

Francesco Molinari returned a 73 for a 6-over score of 222 for the tournament, 22 shots behind the red-hot Westwood.