More telling was his final hole. He thought he had a chance to end his round with a 35-foot birdie putt, and as it broke just right of the cup, he quickly dropped to a crouch and then rose up to go mark his ball. That was the best evidence there was no problem with his back.
"The back's great," Woods said. "I had no issues at all - no twinges, no nothing. It felt fantastic. That's one of the reasons why I let go on those tee shots. I hit it pretty hard out there."
Woods last played at Doral on March 9, when he closed with a 78 while coping with pain in his lower back. He had microdiscectomy surgery on March 31, causing him to miss the Masters and U.S. Open.
His return this soon was a surprise, and Woods was candid in saying that he might not have played if the Quicken Loans National did not benefit his foundation's work with children. He also made it clear he was not risking further injury by playing now.
The only issue Thursday was rust.
"We saw what happened when he found his rhythm," Spieth said, alluding to Woods making three birdies over his last six holes, and missing only one green.