PALM HARBOR, Florida (AP) ― Retief Goosen was about ready to give up.

His lower back was in so much pain that he decided to withdraw next week from Bay Hill so he could get treatment. A double bogey late in his round knocked him nine spots down the leaderboard, which he figured was the end of his hopes to get into the Masters.

One day later, everything changed.

Goosen ran off three straight birdies on the back nine and closed with a tough par from the fairway bunker on the 18th hole Saturday for a 6-under 65 that put him atop the leaderboard with Jim Furyk in the Transitions Championship.

Goosen is No. 52 in the world ranking, and he has to be in the top 50 after next week to avoid missing Augusta National ― along with St. Andrews, his favorite course ― for the first time since 1999.

Or he can avoid the math and just win the tournament, which comes with an automatic invitation.

Those prospects looked dim when he decided Friday to pull out of Bay Hill, and arranged for a protein injection in Virginia on Wednesday. Suddenly, the final round is packed with significance.

“Maybe I’m fighting for that last spot in Augusta,” he said.

Either way, it figures to be quite a battle. Furyk, determined to overcome an atrocious season in 2011, surged into the lead with a 6-iron that covered the flag on the par-3 15th hole and settled 3 feet away for a birdie. He fell back into a tie on the 18th hole with a three-putt bogey up a steep ridge. That gave him a 66.

Furyk was tied for the lead with Bae Sang-moon, the South Korean rookie who lost in the quarterfinals of the Match Play Championship to Rory McIlroy.

Bae escaped with a par on the par-5 14th after his 3-wood found the water by making an 18-foot putt. He wasn’t so fortunate on the 16th, however. He drove left into the trees to protect against water running down the right side of the hole.