Jordan Spieth leads the Masters by four strokes after shooting a 2-under 70 in Saturday’s third round to reach 16 under for the tournament.

It may seem unlikely that anyone can deny Spieth winning his first major, but stranger things have happened at Augusta National, as Greg Norman and Rory McIlroy can tell you after their collapses in the final rounds.

Even Spieth had a lead in the final round of last year’s Masters before consecutive bogeys on Nos. 8 and 9 opened a door that Bubba Watson blew through.

“Last year left a bad taste in my mouth, and I’ve been looking to get back and get some revenge,” he said.

And there’s this: Spieth showed some nervousness Saturday, with several poor shots on 17 and 18, and has had trouble with short putts this week. So there’s always the possibility he could give away a few strokes. But it would likely take a lot of frayed nerves and an exceptional round by someone in the field to catch up to him.

Here are some of the candidates who could catch Spieth in what should be a thrilling final round Sunday:

Justin Rose

Position: Second, 12 under, four strokes behind

Best Masters finish: tied for fifth, 2007

What he said: "Given the choice, you want to be in the last group. You want to see what you are up against."

Why he may win: Already a majors winner, Rose can draw from taking the U.S. Open in 2013. He said he will take the experience of committing to shots during that victory to Sunday's final round. He has posted top-five finishes in each of the majors. He's also streaky, as evidenced by his five birdies on the back nine Saturday, including one from a bunker on 16, that moved him from also-ran into second place. His putting has increasingly improved each round, from needing 31 putts Thursday to 26 on Saturday.

Why he may not: His iron play hasn't been as sharp as his greens in regulation have dropped from 16 on Thursday to 12 on Saturday, but he still is third-best in the field in the category.

Phil Mickelson

Position: Third, 11 under, five strokes behind

Best Masters finish: Winner in 2004, '06 and '10

What he said: "I've won three times here wearing black shirts, so I'll wear a black shirt tomorrow. It also helps me get more aggressive. Studies have shown, like NFL teams, when they wear black, they have more penalties. That's what I need to do tomorrow is play more aggressive.

Why he may win: Because he's done it before. He knows the greens better than anyone in the field, and it's time to show it.

Why he may not: His driving and putting continues to be erratic. After hitting 12 of 14 fairways Thursday, he hit 11 Friday and nine Saturday. He will almost have to be perfect off the tee so that he can attack the flags with the shortest club possible in his hand because his average of 1.746 putts per round is the worst of the contenders.

Charley Hoffman

Position: Fourth, 10 under, six strokes behind

Best Masters finish: tied for 27th, 2011

What he said: "I'm just going to try to keep doing what I'm doing. Hopefully a few putts drop in, and I can put a little pressure on the guys up top."

Why he may win: He has hit 40 of 54 greens, among the best results in the field, so he gives himself a chance to score.

Why he may not: While his driving and fairways hit have been consistent, his putting has gotten worse each round, culminating with needing 31 on Saturday. Plus, he's one of the shortest drivers left playing in the final rounds, which makes it hard to attack the flags.

Dustin Johnson

Position: Tied for fifth, 6 under, 10 strokes behind

Best Masters finish: tied for 13th, 2013

What he said: "(Going to) go out and just try to attack the course. Tomorrow I really need to make a lot of birdies."

Why he may win: Because he's ridiculously long off the tee, leading the field with a driving average of 321.67 yards. His three eagles Friday were a Masters record. It will likely take an unheard of four eagles — or 8 strokes — Sunday to even begin to make up the gap.

Why he may not: While long off the tee he hasn't been particularly accurate, hitting only seven fairways Saturday. Couple that with needing 28 putts and that isn't a recipe for scoring, especially when strokes will be at a premium.