Second-place Louis Oosthuizen of South Africa made an early morning start to his second-round charge at the Masters on Friday while leader Lee Westwood waited to begin six groups later.
World No. 3 Westwood, who ran off four birdies in a row in a front-nine stretch, fired a five-under par 67 on Thursday to take a one-stroke lead over Oosthuizen, the 2010 British Open champion, and Swede Peter Hanson.
Oosthuizen, who birdied four of the last five holes on Thursday to streak up the leaderboard, began his second round on Friday in cool and overcast conditions with a par 4 at the first hole.
"There's still a long way to go, but I feel good," Oosthuizen said. "I'm hitting the ball really well."
Westwood has finished in the top three in five of his past nine major starts but the 38-year-old Englishman is still seeking that elusive first major title in his 55th attempt.
"I came close recently and I have had a good career and all there is to win is a major championship and that is my primary focus now," Westwood said.
Hanson is set to start about an hour after Westwood and alongside three-time Masters winner Phil Mickelson, who opened on 74, and World No. 4 Hunter Mahan of the United States, who fired a 72 on Thursday.
Rory McIlroy, the 22-year-old Northern Irishman tabbed as a Masters favorite after leading three rounds and onto the 10th tee on Sunday last year at Augusta National, is one group in front of Hanson after opening on 71.
"To come off under-par is pleasing," said McIlroy, the reigning US Open champion. "My perseverance and patience paid off."
Tiger Woods, the 14-time major champion chasing the record 18 majors won by Jack Nicklaus, opened with a 72 and will play in the day's penultimate group. He struggled off the tee on Thursday in his first competitive round since snapping a 28-month win drought last month at the Arnold Palmer Invitational.
"I hit some of the worst golf shots I have ever hit out there," Woods said. "I just grinded my way around the course, stayed patient, whatever it took."
World No. 1 Luke Donald of England will be in Friday's last group after opening with a 75.
A field of 95 will be trimmed to the low 44 and level, plus anyone within 10 strokes of the lead after 36 holes, for a weekend expected to be sunny but a bit cooler after damp conditions left the course muddy for the opening rounds.