Published: Dec 01, 2011 3:35 PM EST
Updated: Dec 02, 2011 7:30 AM EST

SUN CITY, South Africa (AP) - Defending champion Lee Westwood birdied the last hole to shoot a 4-under 68 Thursday and share the first-round lead with Masters winner Charl Schwartzel at the Nedbank Golf Challenge.

The third-ranked Westwood holed a putt from near 20 feet on No. 18 for his fourth birdie on the opening day at Sun City. The Englishman also had an eagle three and two bogeys.

Schwartzel also had a productive back nine at Gary Player Country Club, picking up five shots over seven holes coming home after reaching the turn at 1 over.

Top-ranked Luke Donald was the early leader on his return to competition after a five-week break, but a double-bogey six on No. 17 gave him a 70 and a tie for fourth alongside five other players.

Robert Karlsson of Sweden was alone in third on 3 under after five birdies and two bogeys in his 69.

Simon Dyson, fourth-ranked Martin Kaymer, South Korea's Kyung-tae Kim, Graeme McDowell and U.S. player Jason Dufner were all bunched together alongside Donald on 2 under. Just two shots separated the top 10 players.

Most of the 12-man field at the $5 million invitational event struggled through the second nine after a brief rain shower, but Westwood and Schwartzel made late rallies to top the leaderboard.

Westwood set up a strong finish when he landed a 5-iron within six feet on the par-five No. 9 and rolled in his eagle putt. He followed up with birdies on Nos. 10, 15 and 18.

"It was nice to hole that one at the last," Westwood said. "I had it in the back of my mind that Charl was on 4 under and I wanted to be in the last group.

"I played lovely. Nice to make one-putt at the last from about 18 feet because I hadn't made any all day. But tee to green was brilliant."

Schwartzel double-bogeyed No. 9, pushing his tee shot into the right rough and then sending his third into the water in front of the green. But he responded with birdies at Nos. 10, 12, 13, 14 and 16 to come home in just 31 strokes.

"I got cross (on the front nine)," Schwartzel said. "Turning one over, I wasn't happy with myself. I felt like I was playing better than that. And sometimes that's what you need to kick on. I just started firing at the flags.

"I probably got fearless."

Playing for the first time since his blistering finish at Disney World to clinch the U.S. PGA Tour's money list title, the top-ranked Donald had five birdies and a single bogey in a solid round through 16 holes.

But he put his tee shot on No. 17 into the water on the left of the fairway and emerged with a six to drop to a 70 in his first competitive round in over a month.

Karlsson also bogeyed the troublesome No. 17 to end the opening round a shot off the lead after starting with three birdies in his first four holes.

"I played pretty good. A couple of iffy shots but that always happens," said the Swede, who scrambled for a five on No. 17 when it could have been much worse.

"If you don't hit the fairway it's difficult. That's just the way it is. You can't hit it left, you can't hit it short, you can't hit it long. And if you hit it right the green is sloping away from you. It's a difficult hole but a great golf hole."

Dufner, the 2011 U.S. PGA Championship runner-up, had five birdies on his Sun City debut but was pegged back by three dropped shots.

Italy's Francesco Molinari, also in his first appearance at the Nedbank Challenge, chipped in for an eagle three on No. 2 but then faded with four bogeys for an even-par 72 and a tie for 10th with Denmark's Anders Hansen.

British Open champion Darren Clarke was the only player over par after his 2-over 74.