AUGUSTA, Ga. -- The questions about motivation are understandable, given his age, stature and victories during what is now a 23-year professional career.
Phil Mickelson will be 45 this summer, he's already in the World Golf Hall of Fame, and his 42 PGA Tour victories include five major championships.
But there is that issue of just a single top 10 on the PGA Tour -- and just two worldwide, going back to the start of 2014. And his relative lack of decent performances this year.
Of course, this is the Masters and Augusta National, and it's as if Mickelson is refreshed, younger and hungrier.
"He's fired up to play," said Jim "Bones" Mackay, Mickelson's caddie since his first professional event, the 1992 U.S. Open. "He starts coming here about two to three weeks before and just loves it, loves hanging out with the members.
"He loves the place, loves the mojo, loves being out here in this kind of weather late in the weekend. It's just the blue skies, playing in the evening. It really does it for him."
Apparently so.
Mickelson's 67 on Saturday at Augusta National put him in contention to win a fourth green jacket. Yes, he's 5 strokes behind leader Jordan Spieth, and a missed birdie on the 18th kept Lefty from being in the final group with the 21-year-old golfer who has led the entire tournament.
But Mickelson wasn't too worried about that. He found a positive in Justin Rose's moving into the final group.
"In 2012, when I was in the final group watching [Louis] Oosthuizen and Bubba Watson in front of me make birdies, it was a lot harder to follow suit," Mickelson said. "And I was hoping to be in the group in front, and if I can start posting some birdies, I think it's much more difficult to follow than it is to lead."
Of course, Mickelson has a lot of ground to make up, and he's chasing a player in Spieth who will be in the final group for his fourth straight tournament, having won at the Valspar Championship last month before second-place finishes in San Antonio and Houston.
Rose is no slouch, either, as Mickelson knows. The Englishman overtook him two years ago at Merion to win the U.S. Open.
But after rounds of 70, 68 and 67, Mickelson was feeling good about things, just as he was the past August at the PGA Championship, where he finished second to Rory McIlroy -- Lefty's only top 10 on the PGA Tour that year.
"I just love it," Mickelson said of the Masters, which he won in 2004, 2006 and 2010. "It's what I dreamt about as kid, it's what motivated me in the offseason four or five days a week to get up at 5:30 and work out -- dreaming of this, giving myself an opportunity in this tournament.
"Granted, I've got a lot of work to do tomorrow, and I'm quite a ways back. A good round, though, and it could be fun."
Mickelson started strong, with birdies at the second, third and fourth holes and another at the ninth to turn in 32. He bogeyed the 11th but birdied the 13th and 15th and then made an improbable 40-footer for birdie at the 16th that shook Augusta National to its core.
"Crazy," he said. "I mean, it's crazy to make that putt. I'm just trying to two-putt it. But I hit it all the time in practice because it's a spot you want to be if you miss the small section by the hole. I had perfect speed, and it just sort of floated in the side door.
"I remember in 1991 [as an amateur] watching Jack Nicklaus and Tom Watson both hit that putt -- both made it -- and I remember being up in the clubhouse feeling the ground reverberate from that roar. So it's makeable, but it's not an easy one."
Mackay said Mickelson practiced the putt on Wednesday.
"The last thing he did before he left the green was to hit that putt he made," Mackay said. "So he went over and put the ball about five or six feet past pin high and putted that ball up twice, actually, and he was smart to do it."
Mickelson let a shot slip at the 17th, where he put himself in a tough position on the green, then failed to convert a 10-footer for birdie on the 18th.
Still, he hadn't shot back-to-back rounds in the 60s here since 2012, when he finished tied for third.
"He was looking very good. He could have been a couple more [under par]," said Paul Casey, who played with Mickelson. "But I thought he played great. I was disappointed the putt on 18 slid by. It would have been nice to see him maybe in the final group."
No big deal, Phil said.
"I don't think it matters who is close to him," Mickelson said of Spieth. "I think he's playing very good golf, and I think he'll have a good round tomorrow. I think that if he were to come out on top, it would be great to have him in the Champion's Dinner every year. He would just be a great champion.
"He's just a classy guy. He just represents the game very well and at a very young age, and he's just got a lot of game. So if he were to come out on top, it would be wonderful for the tournament, wonderful for the game.
"I'm going to try to stop him, but we'll see how it goes."