SUN CITY, South Africa -- Charl Schwartzel still isn't sure how he did it. He only knows that the rib muscle he somehow tore at the U.S. Open left him struggling with his swing for much of the rest of his season in 2012.
Now that he's playing pain-free again, there are signs that he's nearly back to his best and maybe ready to challenge two-time defending champion Lee Westwood at the Nedbank Golf Challenge at Sun City this week.
The 12-man all-star field is battling for the $1.25 milion winner's purse in the granddaddy of golf's high-profile off-season exhibitions.
Schwartzel said after Wednesday's pro-am that his game was "definitely on the way up."
A tie for third at the DP World Tour Championship in Dubai last weekend and a fifth-place finish at the South African Open the week before fed his growing confidence. They were his first top-10 finishes since hurting himself at the U.S. Open in June.
"I don't even know how I did it," the former U.S. Masters champion said of the injury. "I just basically sat down and I could hardly breathe. Until today, I don't know actually how it happened."
Getting back to his best will still take a little time, Schwartzel said, but he's now completely recovered from the chest injury, which had made him compensate in his swing.
"I don't expect anything from this week," he added, tempering expectations from home fans in South Africa waiting for a first home winner at the $5 million Nedbank Challenge since Trevor Immelman in 2007. "But it's definitely turning. My swing is starting to repeat itself more and more. That is good signs for me."
Schwartzel's obvious caution probably resulted in part from the fact that Westwood has been untouchable recently at Sun City's Gary Player Country Club, winning a second straight Nedbank title last year with the help of a course-record 62 in the third round.
The Englishman is the favorite to to win again at Sun City on Sunday and become the first player with three straight Nedbank titles.
Compatriot Justin Rose, fresh off his own course-record 62 in the final round in Dubai on Sunday, arrives in northwest South Africa as Westwood's likeliest challenger.
Although South Africa's Louis Oosthuizen backed his close friend Schwartzel to "be very strong this week," the Englishmen are the leading contenders.
Westwood's game was perfectly suited to Sun City, Oosthuizen said, while Rose finished second to the all-conquering Rory McIlroy on the European Tour's Race to Dubai money list after an outstanding season from the South African-born Englishman.
"(Westwood's) record is amazing around this golf course," Oosthuizen said, "so you've got to think he's going to be up there. He hits his driver so straight. With narrow fairways, you'll see him take driver on a hole where most guys will probably take a 3-wood.
"Justin, especially after last week, will definitely be one of the guys to look out for. Coming off a 62 ... his confidence is going to be way up there. He's a great player. He had a great Ryder Cup."
Also playing at the Sun City invitational are Westwood and Rose's fellow Ryder Cup winners Paul Lawrie, Nicolas Colsaerts, Peter Hanson, Martin Kaymer and Francesco Molinari, giving the tournament seven members of Europe's victorious team at Medinah.
Sweden's Carl Petterson also made the trip alongside American Bill Haas. Garth Mulroy makes it three South Africans in the field, which is chasing a first prize of $1.25 million.