Oosthuizen ran away with the 2010 Open Championship to claim his first Major title by seven shots and while the 30-year-old has yet to win in the United States, he is eyeing another big trophy in 2013.
"It's all going to come down to the Majors. If I can try and get a Major this year - one, or two even - then the difference will be the Majors, because it's got the big points," Oosthuizen said after his one-shot Volvo Golf Champions victory.
Oosthuizen moved up to a career-high fourth in the rankings and immediately targeted a further rise with only world number one Rory McIlroy, 14-times Major champion Tiger Woods and Briton Luke Donald standing in his way.
"Even if I or Tiger or Luke play really well, Rory is still playing well. It will be tough to catch him," he said.
"Top spot is a tough one. I think Rory is far ahead, so if I can somehow get myself to number two then I can work on trying to get to number one."
The first Major on Oosthuizen's radar is the April 11-14 Masters, on an Augusta course he likes after losing in a playoff to Bubba Watson last year. However, the South African is not playing up his chances.
"I'm just going to try and handle it as a normal tournament. I never like to have big expectations before the tournament," he said.
"I like to start the tournament and then if I feel my game is there and I'm playing really well, then you know, everything starts ... that attitude where I feel I've got a good chance this week."
Oosthuizen will also be determined to land a first title in America after two second-place finishes in 2012, his Masters heartbreak and at the Deutsche Bank Championship in September when McIlroy overhauled his 54-hole three-shot advantage.
Oosthuizen's albatross at the par-five second hole at last year's Masters - only the fourth one ever recorded at the year's first Major - was voted European Tour shot of 2012 on Monday.
"It has to be the most memorable shot of my career so far," said Oosthuizen of the 253-yard four iron that landed at the front of the green and ran all the way across the putting surface before dropping in the cup, triggering huge roars.
