"The ball, the scorecard, they don't know the difference in age," he said. "It's a fun challenge for me to get back to competing at the highest level."
So far, the old man is doing alright. Mickelson leads the PGA Tour in scoring average at 69.033. In 23 prior seasons on tour, Mickelson has never won the Byron Nelson Award or Vardon Trophy given to the player who leads the season in scoring average.
To say Mickelson is invigorated would be an understatement. Since officially making the switch after a disappointing 2015 season to new swing coach Andrew Getson, Mickelson's game has been methodically rounding into shape.
"I just know that it's the best I've driven the ball, the easiest I've driven the ball," he said. "Misses are minuscule. Speed is back. Iron game is sharp. And I'm hitting fades, draws, high, low, everything at will without much thought. It's becoming much more instinctive. Game's starting to be instinctive – I think that's probably the best way to say it, where I don't have to think about the technique or the mechanics of anything. I just kind of look and react. And when I'm playing well, golf is an instinctive sport. I look, I see the shot I want to hit, I feel the shot I want to hit and then I just execute."
Those instincts had Mickelson in the mix again at Doral, where he tied for fifth place on Sunday. Already this year he's finished third, 11th and second – a runner-up to Vaughn Taylor at Pebble Beach when his 5-footer to force a playoff lipped out on the final hole.
It's not the result Mickelson wanted, but it's not results he's worried about right now. That only matters when everyone gets to Augusta National and Oakmont, where he'll try again to complete his career slam with the elusive U.S. Open in June.
"The tough thing for me right now is to not focus on results, to just be patient," said Mickelson, who has been sitting on 42 career tour victories since his British Open triumph at Muirfield in 2013. "Because this is the best I've played in a long time, and the results will come if I'm patient.
"Patience for me is regarding the results, you know, trusting that the results will come if I continue to play the way I'm playing. And sometimes we kind of force the issues and we want instant results, instant feedback. I've had some pretty positive feedback, but I'm probably pushing the issue a little bit. I just need to settle down and let it happen, because this is the best I've played in a long time."
That "best I've played in a long time" refrain is driving Mickelson's enthusiasm. It's also what is driving his work on the greens.
There is another villa at the Doral resort with Phil Mickelson's name embossed in gold lettering across the front of it. But Mickelson requests a room every year in the one named after Tiger Woods so he can be nearer the practice green and the range.
The resort has kindly obliged to replace the Tiger pictures that adorn the walls in Phil's room with a few of the left-hander to make him feel at home.
Now he feels at home with his new swing and keeps working on a claw grip for short putts that will ultimately determine whether a 45-year-old can beat the McIlroys and Spieths and Bubbas at Augusta and the other major stages.
"I was nervous about the first month – how the results were going to go, was I going to play at the level that I thought I was ready to play at," Mickelson said. "And now that I am, now that I'm in contention, now that I feel much calmer and more relaxed playing and showing up on the golf course, I know it's a matter of time. It would have been great to have gotten a victory early on the West Coast, but I just feel like each week is going to provide another opportunity, whereas in the past, I felt like I was kind of hit or miss when I would show up."
Mickelson is emerging from the darkness of the longest winning drought of his professional career. He's approaching 1,000 days with a victory, grinding into the night to find the light at the end of the tunnel.
Even with so many great players less than half his age making most of the golf headlines these days, only a fool would count Mickelson out as the Masters approaches.
"So win, lose or what-have-you, it's not really affecting the confidence that I have or the direction that I feel like my game is going," he said.