AUGUSTA -- Fred Couples is trying to believe, just like many of his fans who are walking the grounds of Augusta National, that he can win the Masters.

Though that walk included numerous stops to stretch his back, Couples posted an eye-popping and gallery-pleasing 68 on Friday and is 5 under par entering Saturday's third round.

Can the 51-year-old Couples trump the 25th anniversary of Jack Nicklaus' win, the win that established the Golden Bear as the oldest victor in Masters history?

"Six years ago ... maybe," he said. He unconvincingly added, "Could I win? Of course."

But he said it's going to take something extraordinary for him to add a second green jacket to his closet. He estimates he would need to get to 14 under.

Phil Mickelson, who played a practice round with Couples on Wednesday, said it's not unrealistic that Couples could win because his putting continues to improve.

"It would be a pretty surprising feat, but not that surprising," the defending champion said.

But Couples doesn't like his chances for two reasons: the fact that he's old enough to play the senior tour (he does by the way), and his cranky back.

He said it didn't seem unbelievable that Nicklaus surprised most everyone when he won his sixth green jacket in 1986 at the age of 46. He said it would have been totally unbelievable had Tom Watson won the British Open two years ago at the age of 59. He pointed out that his Masters win came over Raymond Floyd when Floyd was 49.

"I'm just glad [Floyd's] not the oldest winner," he joked.

He said it's not hard for someone in the senior set to score one good round. It's physically difficult for someone to do it for four consecutive rounds. He implied the same is true, though the reason is different, for players from 20-22. They may be able to hit it long, but most don't have the course knowledge.

That's one advantage he has at Augusta. He said here and Riviera are probably the only courses on which he can still contend. He knows both. Because he can still hit the ball a long way -- he regularly outdrove playing partners Steve Stricker and Luke Donald -- he can reach the par 5s in two and have medium or short irons into the par 4s.

But Augusta isn't some fountain of youth for Couples as it is for Mickelson, who said he gets re-energized every time he drives down Magnolia Lane.

"I'm not ever energized," he said, but he added there is an excitement when playing the course.

Now, if his back can hold up.

Watching him swing a club is like watching your favorite grandfather clock: The tempo is pure and reassuring after so many years, but you wonder how much longer can it go before breaking down?

Although he was the oldest player to make the cut at his hometown Shell Houston Open last week, he told one writer there that his back was "shot." And that he was going into this week at Augusta "to have some fun." Obviously the expectations were low.

He received some shots last week that have made his back feel "so-so." After Thursday's first-round 71 he said he was in a lot of pain, so much so that he couldn't stand still. No matter the "toothache" type of pain, he predicted that he was going to shoot something low Friday. He didn't know what, but he said it would happen.

His intuition proved correct.

He made birdie putts of one foot on No. 2, 15 feet on No. 4, six feet on No. 7 and 15 feet on No. 12.

He laced a drive on 15 and took out a fairway wood to try to reach the green on the 530-yard, par-5 hole.

Standing in the gallery to the right of the fairway, Doris Hearty whispered "Go Freddie," as he examined the swaying pines to gauge the wind.

"I've loved Freddie for years," she said. "His swing is so fluid."

His shot scurried through fringe on the back of the bunker to the right of the green and came to rest in the second cut. He putted to 10 feet and sank the birdie.

His tee shot on 16 landed 15 feet from the pin, placed on the right, and spun back to the front of the green. He three-putted for his only bogey.

As the gallery began to notice Couples' steady climb up the leader board, they began to abandon their seats in the bleachers to follow him up No. 17 and down No. 18.

During those final holes he often twisted to the left and right in the familiar golfer's dance to keep his back loose while his playing partners prepared to shoot.

"He's still struggling to get around out there," Davis Love III said Friday. "Last week he was playing well, but then his back wore down. Guys like him and Scott Verplank have never had a chance to show just how good they really are because of their injuries."

Couples said he will have no problem playing Saturday and Sunday, even though it's awkward to play golf in such pain.

He was a dark-haired heartthrob the last time he won the Masters. Now, with a bit more gray around the temples, how would "Boom Boom" describe his chances of winning the Masters?

"Retiring is what it would be," he said. "I would be gone. You know, it would be the biggest upset in golf history."