One was a putt from 17 feet.
The other was a drive that traveled 341 yards.
Down to his last shot, Johnson watched his 17-foot par putt stay on the high side of the hole and thought for sure it would miss. He took two steps of hope to the right, then pumped his fist in a rare show of emotion when the ball swirled around and dropped in the back side of the cup for a 4-under 66 to force a playoff.
Given new life, Johnson relied on his strength and powered a drive over the lake to the far edge of the fairway. It was the longest drive all week on the 18th hole, and it left him a 60-degree wedge to 4 feet for birdie and a victory he badly needed.
The No. 1 player in golf finally looked the part again.
"It was fun to be in the hunt again and know that my game is going to hold up under pressure," Johnson said.
Spieth lost for the first time in six tries when leading by two shots or more, and there wasn't much he could do, except take back that tee shot into the water on the par-3 sixth hole after building a five-shot lead. Johnson played bogey-free over the final 29 holes.
"I didn't lose the tournament," Spieth said after closing with a 69. "He won it."
It was great theater between Johnson and Spieth, good friends who now are No. 1 and No. 2 in the world.
"I thought that was a fun show," Spieth said. "I was hoping it wasn't going to be that much fun."
Johnson made up a five-shot deficit in five holes, and the two battled along the back nine with big shots and big moments.
They were tied on the par-3 17th when both hit into a bunker, and Johnson blasted out to 4 feet with an easier shot and angle to the hole. Spieth had 18 feet for par and knocked it in, like he always seems to do.
On the closing hole, Johnson showed the kind of golf IQ that belies his simple outlook on life. After he sliced his drive up the hill and into a nasty lie in the rough, he chose to lay up, instead of trying to hammer a shot to an elevated green.
But he made it pay off with a par that got him into the playoff, after Spieth lagged a 75-foot putt perfectly to get his par.
They finished at 13-under 267.
Johnson was angry with himself after his tee shot in regulation for not taking it over the water, even with a light wind in his face.
"Right after I hit my drive, I was like, 'What am I doing?" Johnson said. He told his caddie, brother Austin Johnson, that if they got into a playoff, he wouldn't make the same mistake twice. It took the most clutch putt Johnson has made in his career, and he blasted his best drive of the week.
Spieth knew it was going to be tough when the two returned to the tee and felt the wind switch in their favor.
"I was hoping he was not going to notice that," Spieth said.
Johnson won for the first time since he wrenched his back during a spill down the stairs that knocked him out of the Masters and derailed his dominance in golf. He had won three straight tournaments against strong fields until that injury.
"I feel like the game is finally back in form like it was before the Masters," Johnson said.
Of his 16 victories, this was the first time Johnson faced a must-make putt on the final hole, and he delivered a par putt that even Spieth thought was going to miss on the high side of the hole.
"But his body language was hanging in," Spieth said. "I'm like, 'Does that really still have a chance?' And it came around and lipped it. My initial thought was, 'I just did that exact thing to him the hole before."
The Northern Trust never looked as though it would contain so much drama.
Spieth began with a three-shot lead, and he stretched it to five shots with a 30-foot birdie putt on the fifth hole.
Five holes later, the two were tied.
Spieth's tee shot on the next hole banged off the rock wall and into the water on the par-3 sixth, and he made double-bogey. On the ninth hole, Spieth took three putts from just off the left side of the green, and Johnson made a 7-foot birdie putt for another two-shot swing.
No one else really had a chance.
Jon Rahm (68) ran off three straight birdies early on the back and briefly was one shot behind, though he had stronger holes ahead of him and fell back. Jhonattan Vegas (65) was within two shots after playing the scoring holes. They tied for third, four shots behind.
Otherwise, it was a matter of who finished among the top 100 in the FedEx Cup to move on to the TPC Boston next week for the second playoff event.
Bubba Watson shot a 70 and tied for 10th to become one of eight players to qualify for the second playoff event in all 11 years of the FedEx Cup. David Lingmerth and Harold Varner III also moved into the top 100. That marked the fewest players outside the top 100 to advance since 2007.
Johnson moved to the top of the list. Spieth is right behind. They will play together in the opening two rounds next week in Boston.