'Today, I'll obviously know what Patrick Reed is doing, but apart from that, I'm going to set myself a target, try to get to that, and hopefully it's enough'.
The 24-year-old Texan turned in one of the greatest closing rounds in Masters history, shooting an 8-under 64 that pushed him into the mix after he started the day with a daunting nine-shot deficit.
"My poor start yesterday I didn't really think could determine the outcome of the tournament for me, " Spieth said. "That's all I wanted to do".
Fowler was also on fire in the final round, firing in six birdies on his way to a 67 that rocketed him to 15-under.
"I'm out there to play the golf course", Reed said.
Spieth bogeyed the last as his title hopes dwindled so then it went to Rickie Fowler.
The former Augusta State All-American is 18 holes away from his first major championship, just 10 minutes away from where he played the last two years of his college golf, leading the Jaguars to back-to-back NCAA Division I national titles. He sank the comeback effort and pumped his fist in celebration.
McIlroy earned the early advantage with a birdie at par-5 3rd hole but Reed answered at the 5th to get the match back to all square.
"I feel like I'm hitting the ball well enough. I feel like I've got nothing to lose".
The duo, who famously went head-to-head at the Hazeltine Ryder Cup back in 2016, will go out as the final group as Augusta looks to crown its latest victor (7.40pm BST). A fist-pumping 20-footer for birdie on the 18th gives the Irishman momentum to duel with Reed the way they did at the Ryder Cup two years ago.
Those eagles increased Reed's total to five this PGA TOUR season. With a tap-in birdie at the par-5 13th, Spieth whittled another stroke off Reed's lead.
And he had no sooner moved to even par for the tournament with a birdie at 17 than he produced a bogey at the last.
Spieth clipped a tree branch off the 18th tee and needed three to reach the green, where he missed an 8-foot par putt that would have seen him match the 18-hole course record. They have been playing each other since junior golf and Thomas has been trying to claim the No. 1 spot in the world that Johnson now holds and Spieth used to own.
Instead, he made history of a different kind in two ways no one was really considering. It was a birdie, though, and the lead was just one. Justin Thomas (70), Jordan Spieth (71) and Dustin Johnson (71) all are at least nine shots behind.
"It was possibly the highest score I could have shot today", Woods said.
"All in all", he said, "it was a bittersweet ending".
He curled in a 14-foot eagle putt at the 13th, then saw his chip at 15 hit the green and race toward the hole, striking the pin and dropping in.
Woods, restricted to only a Champions' Dinner appearance the past two years at the Masters, played alongside England's Ian Poulter in yesterday's third round and take his best shot at a charge up the leaderboard from his share of 40th place.