"It's not going to be easy", Garcia told Sky Sports.
"That gets overlooked", said Stewart Hagestad, the amateur from Deepdale Golf Club on Long Island who is in this Masters and is a friend of Spieth from when they played junior golf against each other.
Rose, who has a U.S. Open title and an Olympic gold medal, is seeking his first green jacket.
Jordan Spieth found himself in the pine straw under the trees on the par-five 13th, a position similar to that from which playing partner Phil Mickelson played a brilliant shot on his way to the title in 2010.
And now, after a near-flawless 68 - the only blemish being a three-putt bogey at 16 - this will be a new experience, this whole come-from-behind thing. On the par-five 13th on Saturday, he weighed the merits of laying up before saying to caddie Michael Greller, "What would Arnie do?"
Spain's Sergio Garcia, who has yet to win a major tournament in 73 starts, started Saturday in a four-way tie for the lead.
Forty times in the 80 years of the Masters, the third-round leader or co-leader has won the tournament. I had my head down and knew I was creeping up on the leaders.
Justin Rose. Sergio Garcia.
The 28-year-old has had some big moments in golf, winning prestigious tournaments like the 2012 Wells Fargo Championship and The Players Championship and Deutsche Bank Championship in 2015.
If you are into a Renaissance of English golfers, then Rose is your man. "That's all you want".
"I mean, I guess the golf course was Tiger-proofed at one point", Spieth said. Pieters was first to leave the rarefied air with a bogey at the first, but it was the 11th that removed him from the list of viable contenders. I've started to hit some quality iron shots and that has some up some birdie opportunities and today I felt really comfortable with the putter.
"We wanted to shoot four-under today and thought if we did the lead would move to six or seven and I'd creep on it", said the resurgent Spieth. I want to give myself a chance for that to be enough.More news: James Hinchcliffe rebounds from crash to take Long Beach Grand Prix
And he was in good shape on the par-4 fifth hole. Both are at 6-under par 210.
Rickie Fowler one stroke back. The final group will be Garcia and Rose, each with his own accomplishments and burdens. "I didn't know going into my first one if I would have five chances in my life", Spieth said.
He wasn't going to layup, not on this hole and not in this tournament, because falling behind by 10 strokes at Augusta National has brought out a different side of a golfer who, at just 23, plays this course better than nearly anyone has in history. "Great shots were rewarded, but mid-irons out of the rough were hard". Two holes later, he almost holed a wedge from the 15th fairway.
Lurking two shots adrift, Spieth - who has finished 2nd-1st-2nd in his three Masters appearances - claimed his final round approach would be an aggressive one. "We fought back tremendously to have a chance to win this golf tournament and no matter what happens at the end, we will have a chance to win with a really good round tomorrow". Spieth could have been forgiven for playing safe, but smashed a long iron onto the green from 230 yards and narrowly missed the eagle putt.
Having fired four birdies through the first 17 holes, the Englishman recorded his only dropped shot on the 18th hole for a 69 that leaves him at level par for the championship, a score he feels leaves him just too far behind the leaders. He is now just two strokes off the lead.
Going into the final round six shots adrift and with 10 players to leapfrog - and especially given the quality of those ahead of him - makes for a tough assignment.
Also challenging were Australian Adam Scott, the 2013 victor, at three under, with 2011 champion Charl Schwartzel of South Africa another shot back.
Lee Westwood of England also shot 68 and is one more down in a tie for ninth with Masters rookie Thomas Pieters of Belgium, who struggled to a 75.
It looks like Rory McIlroy's career Grand Slam will remain incomplete.
His back nine was filled with pars except on the two par 5s.
Garcia probed around the leaderboard all day while watching others make bogeys and birdies around him.