Lefty turns 42 in June and remains one of the most talented golfers in the world. He has 39 victories in his brilliant career, including four major championships.
His streak of victories in eight consecutive seasons heading into this year is the longest active on the PGA Tour, but he has only two titles in his last 43 starts on the circuit dating to 2010.
Mickelson, who tied for 49th in the Humana Challenge and missed the cut in the Farmers Insurance Open to start this season, is out of the top 10 in the World Golf Rankings for the first time since 2004.
"Phil has had a lot on his mind the last couple of years with his wife and his mother (battling cancer), and he’s in his 40s now," Chris DiMarco told pgatour.com. "That’s when things that are important to you change, and that’s not a bad thing. In Phil’s case, he’s achieved so much, but the desire is still there."
Mickelson, who will be inducted into the World Golf Hall of Fame in May, plays this week in the Waste Management Phoenix Open, which he won in 1996 and 2005 at TPC Scottsdale, not far from his alma mater, Arizona State.
Of course, Lefty also has had to deal in recent years with psoriatic arthritis, and although he claims it’s being handled by medication, he faded several times late in tournaments he had a chance to win last season.
His final-round scoring average of 70.47 was the highest of his career, and that’s not going to help him reach the two big goals he has set for the rest of his career.
"I would like to get to that magic number of 50 wins that few players have done," Mickelson said last year. "But, also, finally getting that U.S. Open win would mean a lot to me, as well as would a British Open win, which would conclude the Grand Slam.
"I came close at the British Open (last year) at Royal St. George’s. I’ve had five seconds at the U.S. Open. I am going to try to take the knowledge I’ve gained over the years that led to those good performances and see if I can get over the hump."
Mickelson has only one victory since turning 40, the 2011 Shell Houston Open, and to reach 50 he will have to emulate Vijay Singh, who has won 22 times since reaching the big 4-0, or Sam Snead, who did it 17 times.
Phil the Thrill has captured three Masters titles and the 2005 PGA Championship but is haunted by seven runner-up finishes in the majors, including those five in the U.S. Open, one in the PGA and last year’s second place at the Open Championship.
"If I was Phil Mickelson, I would look at five runner-ups as very, very disappointing," Curtis Strange, a two-time U.S. Open champion, said last year. "You have to try to take a positive out of it, but when you have his amount of talent and his ability and his record, you know, not winning when you have a chance to win is disappointing.
"And there is no way else to look at it. I felt for him every time. But he’s had opportunities, and he just hasn’t come through. I think he certainly would look at it as a black eye right now."
It certainly gets more difficult to win a major after 40, but Julius Boros captured the 1968 PGA Championship at 48, Jack Nicklaus won the 1986 Masters at 46 and last year Darren Clarke ended years of struggle by winning the Open Championship at 42.
Lefty might have more major titles in his future, but for now he’s known for those that got away, and he’s not alone.
"When we think of Jack Nicklaus and Tiger Woods, we think of their accomplishments," commentator Frank Nobilo said on the Golf Channel two weeks ago during the Humana Challenge. "When we think of Greg Norman and Phil Mickelson, we think of what might have been."
Norman captured the Open Championship in 1986 and 1993, his only major titles, but had eight runner-up finishes in the majors. Included were a Masters stolen from him in 1987 by Larry Mize’s miracle chip, and a PGA that Bob Tway won by holing a bunker shot in 1986.
Mickelson and Norman have had their signature breakdowns, too.
The Great White Shark took a six-stroke lead into the final round of the 1996 Masters but collapsed with a 78 and finished five shots behind winner Nick Faldo.
Lefty took a one-stroke lead to the final hole of the 2006 U.S. Open at Winged Foot but sliced his tee shot onto a hospitality tent. After slapping the ball from rough to sand to green, he took a double bogey and wound up one stroke behind champion Geoff Ogilvy.
Of course, that led to his famous quote: "I am such an idiot."
The good news for Lefty is that even though his window is starting to close, he still has some precious time left.