Nicklaus, a six-time Masters champion, played a practice round Sunday with his three oldest sons and played again Thursday with his youngest son and Arnold Palmer.
'While I don't know if my golf game is good enough or not, I feel good enough physically, and I am hitting the ball long enough to play the golf course,' Nicklaus said on his Web site. 'Now, it's up to me.'
The 63-year-old Nicklaus did not say what he shot in either round, but did say the score was irrelevant.
He skipped the Masters last year because of lower back problems. Nicklaus is on a new diet that has left him trim and fit. The only thing left to decide was whether he could handle a course that is 7,290 yards - 305 yards longer than he last played in the Masters.
During practice rounds last year, he hit eight fairway metals into the par 4s.
'Last year, I hit driver, 3-wood into No. 1, and this week I hit 6-iron into that green,' Nicklaus said. 'On (No.) 9 last year, I hit 4-wood into that green, and I hit 8-iron Sunday.'
Even with a new tee on the fifth hole that added 20 yards, Nicklaus said he managed to reach that green with a 6-iron.
'When you can hit mid-irons into those new par 4s, that's long enough for me to play the golf course,' Nicklaus said. 'It's certainly not Tiger Woods' length. That's not even quite Sam Saunders' length.'
Saunders in the 15-year-old grandson of Palmer, who played with them Thursday.
Palmer, who played in his last Masters a year ago, persuaded Nicklaus to play in the Bay Hill Invitational last week. Nicklaus had rounds of 82-76 to missed the cut.
'If this is any indication here, I can't play anything,' he said.
Still, most believed Nicklaus would return to Augusta National, the course he dominated over three decades.
This year is the 40-year anniversary of his first green jacket, which Palmer slipped over his shoulders. Nicklaus also won in 1965, 1966, 1975 and 1986, when he was 46.
Nicklaus last contended at Augusta National in 1998 when, despite a degenerative left hip, he made a Sunday charge and tied for sixth to become the oldest player to finish in the top 10 at the Masters.
'I didn't want to go back there unless I thought I could contribute to the field and be competitive,' Nicklaus said. 'I certainly don't think I'm going to be competitive enough to win a golf tournament, but if I really play well, I might have a decent finish.'
Nicklaus has said he would consider the top 10 a good goal if he played well.
Since turning 50, Nicklaus has made the cut nine of the 11 times he has played the Masters.