The 22-year-old Texan has now held the outright lead for a record seven consecutive rounds and if he can hold on for one more day will join Tiger Woods, Nick Faldo and Jack Nicklaus as the only men to claim back-to-back Masters wins.
Spieth, who began the third round with a one-shot advantage, ended it in the same position after a wild afternoon at a windswept Augusta National, carding a one-over 73 that featured two double-bogeys on the back nine, including one at the 18th.
An 80th Masters that had looked ready to turn into a coronation with Spieth holding a four-stroke edge with two to play but will instead be up for grabs with an eclectic mix of challengers, including a Masters debutant, a 58-year-old former champion and a 24-year-old Japanese sensation all lurking.
American rookie Smylie Kaufman, who still lives with his parents, had the lowest round of the day, returning a three-under 69 to join Spieth in an unlikely final pairing.
“That wasn’t a fun last couple holes to play from the position I was in,” said Spieth, who also had a bogey at 17 to surrender three shots over his last two holes.
“It’s not going to be fun tonight for a little while, and hopefully I just sleep it off and it’s fine tomorrow. I imagine that will be the case. It was tough.”
Sitting two off the pace is evergreen German Bernhard Langer, a two-time Masters winner who showed he still knows how to get around a tricky Augusta layout, carding a two-under 70, and Hideki Matsuyama, playing in his fifth Masters, who had 72.
Australian world number one Jason Day, the pre-Masters favourite who struggled to find consistent form through the early rounds, finally emerged as a contender as he rocketed up the leaderboard with a 71 to finish three shots off the pace.
The third round began with the spotlight firmly on two of golf’s charismatic young guns, Spieth and McIlroy forming one of the most anticipated final pairings ever featured at the year’s first major.
Tracked by massive galleries, the dynamic duo had all the credentials of an all-star pairing with the Texan and the Northern Irishman having claimed four of the last six major championships played.
But the marquee matchup failed to deliver on the promised suspence as Spieth held firm and McIlroy quickly faded, slumping to a five-over 77 to fall five strokes back and leave his bid for a career grand slam on thin ice.
Instead it was Langer, Matsuyama and Kaufman who stole the show with masterful displays of golf in challenging conditions.
Kaufman, level with six to play, produced a sizzling finish as he drained birdie putts at the 13th, 14th and 16th.
“I’m driving the ball really well right now and if I’m going to get on the greens just as much as everybody else, I think that I’ll have a pretty good opportunity to be in contention,” said Kaufman.
“That was the goal coming into the week, just get in contention. And now that I’m here ... kind of re-adjust the goals a little bit and try to win tomorrow.”
Langer, who won both his Masters titles before Spieth was born, also made a stirring late charge with three consecutive birdies from the 13th.
He gave one back at the last but will still enter Sunday with a chance to become the oldest ever major winner and take the torch from American Julius Boros, who was a full decade younger when he won the PGA Championship at age 48.
“I believe I can,” declared Langer, when asked if he can win a third Masters. “If I play my best, I can shoot four-or-five under tomorrow… but so can Jordan Spieth.
“I said earlier on, sooner or later, it’s going to happen. One of the over 50s is going to win a major.”
Original source: Spieth stays top despite late stumble