HAVEN, Wis. -- For Phil Mickelson, it's been a career filled with what-ifs.
What if Payne Stewart didn't make that dramatic 15-foot par putt in the 1999 U.S. Open at Pinehurst No. 2, leaving Mickelson one stroke out of a playoff?
What if David Toms didn't put the perfect stroke on a 12-foot par putt of his own at the 2001 PGA Championship, edging Mickelson by, yet again, one shot?
But at this year's Masters, Hard Luck Phil finally got a little redemption of his own, holing an 18-foot putt on the 72nd hole to win his first major after flirting with so many titles and falling short each time.
Which leaves us thinking: What if Chris DiMarco didn't give Mickelson such a good read on the putt? What if the ball didn't drop in the hole on its final rotation? What if Lefty didn't win the Masters?
How would you feel then, about that three-putt from five feet in this year's U.S. Open? Or Mickelson's failure to hold the lead on the back nine of the British Open?
You'd probably feel about the same way Mickelson does.
"Oh, I think it would have been quite a bit tougher, absolutely, having those close chances," said Mickelson, who finished second to Retief Goosen at Shinnecock Hills and one shot out of the Todd Hamilton/Ernie Els playoff at Royal Troon. "Having the lead in the final nine and not winning would have been a lot tougher had I not won the Masters."
Perhaps Mickelson's Masters win gave him the one thing he was always searching for and could never attain. Perhaps it elevated him to elite status among the golfing community and a title relegated to American heroes -- the People's Champion.
Or, perhaps, Mickelson's Masters win took the edge off just enough that he knew in the two subsequent majors that he didn't need to win, he only wanted to. Perhaps the first major victory took away the killer instinct to snare the next one.
Either way, Mickelson knows what he's missed out on.
"I'm three shots away from having the Grand Slam," said Mickelson, who could ostensibly lock up Player of the Year honors with a win this week in the PGA Championship at Whistling Straits. "Certainly I think about that. I don't dwell on it. What I try to do is think about what I can do to make up those three shots."
Mickelson, along with the rest of the world, knows he can't get those three shots back. Now, he admits, he must search for ways to find those strokes before it's too late once again.
"I'm constantly thinking about how to salvage a half a shot here or there or even a quarter of a shot," said Mickelson, whose 68.60 scoring average this season is tops on tour. "If I can improve my 72-hole total by three or four shots, it would be a world of difference. That's less than a shot a round. Those are the things I'm trying to improve upon.
"I've been able to do it well this year, but had I been able to do it just a little bit better, it could have been an incredible year."
A great year for Mickelson? Absolutely. An incredible year? What if ...
Jason Sobel is ESPN.com's golf editor. He can be reached at Jason.Sobel@espn3.com.