Instead of smashing a driver and a locker, he demolished the front nine at East Lake on Thursday with five birdies over a six-hole stretch that carried him to a 6-under 64 and a one-shot lead over Masters champion Adam Scott.
It was a big turnaround from Monday at Conway Farms, not only on his scorecard but between the ears.
''I just needed to realize the world is a good place again,'' Stenson said.
Stenson was playing his seventh tournament in 10 weeks when the BMW Championship was extended a day by rain. He slammed his driver so hard into the ground on the final hole that the head snapped off, and then he took out his frustrations on his wooden locker at Conway Farms.
Playing all 18 holes at East Lake for the first time, it looked like he couldn't miss. On the opening seven holes, he had only one iron shot outside 10 feet, and he converted five of them for birdie.
''I really knew I had to be in a good frame of mind coming out there if I wanted to play good golf this week,'' he said. ''As some of you noticed, I wasn't that on Monday when I finished up in Chicago. So it was a good turnaround mentally. I stayed very level-headed – kept the head on, both myself and drivers, and played a great round of golf.''
Tiger Woods didn't make a thing.
Woods missed a short birdie putt on his opening hole that set the tone for the day. He was the only player in the 30-man field to go without a birdie. On the par 5s, Woods three-putted for par on No. 9 and missed a putt just inside 10 feet on No. 15.
It was only the seventh time in his PGA Tour career – and third time at East Lake – that he went an entire round without a birdie. Woods shot a 73, matching his highest opening round of the year. He walked past reporters without comment.
Scott did his damage on the back nine, making six birdies in seven holes for a 29 that had him tied for the lead until Stenson finished off his remarkable round with a 5-iron from 223 yards to 4 feet for birdie on the par-3 closing hold.
''It was a tale of two nines, there's no doubt,'' Scott said. ''I missed three greens with wedges on the front nine and wasted all my chances to score. I hit two good shots into 10 and rolled a putt in, which calmed me down. And then I just went and played, and played the way I felt I could.''
Stenson, the No. 2 seed and the hottest player in golf over the last three months, and Scott (No. 3) only have to win the Tour Championship to capture the FedEx Cup and the $10 million prize. Even more is at stake for Scott, who would be a strong candidate for PGA Tour player of the year if he were to win this week. That would give him three wins, compared with five wins for Woods, though Scott would have a major and the FedEx Cup.
''There haven't been too many guys who have been in the position the last 12 years to even warrant thinking about it,'' Scott said. ''So it's an opportunity that might not come along too often. I'm going to be working hard to try and make my case for it.''
More than feeling better about his attitude, Stenson was helped by feeling no pain in his left wrist.
He suspects he slept on it wrong last weekend, and it reached a point where it hurt to hold a toothbrush. He played only nine holes of practice – the front nine – on Tuesday and iced his wrist and took anti-inflammatories. It seemed to have worked.
The biggest change was his attitude.
Stenson is known for public displays of frustrations – remember that poor tee marker at Carnoustie in 2007? – but this was peculiar because he had just won the Deutsche Bank Championship in his previous tournament. That capped off an amazing summer that began with four straight tournaments in the top three, including two majors and a World Golf Championship. He said he apologized to the club and told the locker-room attendants to keep in contact, presumably so he can pay for the repairs.
Why so much anger so soon?
''I can tell you don't have much experience with Swedes, do you?'' Stenson said, handling it with his dry humor. ''No, I'll tell you I've always been a bit of a hot-head, and I just haven't been able to get any rest. I was looking forward to that Monday back home and lying on the couch – the kids in school and me just doing nothing, and I ended up playing golf again on that Monday. I was just tired, and I pushed myself over the edge there.
''That's not the best place to be and not the best frame of mind to play good golf,'' he said. ''I'm really delighted with the change I made to today.''
In his Tour Championship debut, his head was in the right place, his wrist felt fine and Stenson was on top of his game like never before. He had one stretch of three birdies all within 4 feet, capped off by a 6-iron from 207 yards over water to a right pin that settled a foot away.
And he did it all in the presence of Woods, the No. 1 player in the world.
''It's a nice feeling to hit those kind of shots playing with the world's best player,'' Stenson said. ''Normally, it's him who does it to everyone else. But it was kind of nice to throw a couple at him.''