That he can play great golf is unquestioned. He had won four major titles and was in the mix until the end of the previous major, the U.S. Open last month at Merion near Philadelphia. He finished second there, as he had five times previously in that tournament without a victory. He has won the Masters three times and the PGA Championship once.
So, after yet another U.S. Open slipped away, knowledgeable Mickelson watchers set their sights on next month's PGA in Rochester, N.Y., as his next likely chance.
Little did they expect that he would come to Europe, win his first-ever links-course title in the Scottish Open, and come from out of nowhere on the Sunday of the British Open to win at Muirfield.
His closing round of 66, to go with 69-74-72, made him the only player to finish under par in the tournament. He caught the field midway through the back nine and finished it off with four birdies in the last six holes to finish at three-under 281 and win by three strokes.
This was his 20th British Open. In all but two, he was a non-factor, giving him the reputation of a guy who didn't feel comfortable, or play well, on British links courses. He didn't disagree. In his best previous British Open effort, in 2011 at Royal St. George's in Sandwich, England, he hit his approach shot into the bleachers on No. 18 and, as the runner-up, got to stand next to champion Darren Clarke at the awards ceremony.
That figured to be as good as it was going to get in British Opens for Mickelson.
He made a 10-footer for birdie on No. 13, taking him to one under, and never looked back.
"I thought right around even par or maybe one under would be enough to win the championship," he said.
That said, he birdied three more, including the door-slammer on No. 18, a slippery 15-footer that rolled true.
Woods never got traction. He started the day in the second-to-last pairing at one under par and finished with a 74, three over for the day and two over for the tournament. He bogeyed three of the first six holes and never contended.
He has gone five years, back to the 2008 U.S. Open at Torrey Pines, without a major title. He said his disappointment was eased a bit by Mickelson's sensational round.
"I think, if it does feel any better," he said, "it is that Phil got to three [under]. . . . That's a hell of a number."
Westwood, 0 for 62 in majors now at age 40, started at three under and with a two-shot lead. He also started with the much-ballyhooed intangible of recent British sports momentum — Andy Murray winning Wimbledon and Justin Rose winning the U.S. Open to end British droughts.
But karma made no putts, and Westwood went from a promising birdie at No. 5 to a four-bogey slide downhill that left him shooting a final 75 and sharing third with Adam Scott and Ian Poulter at one-over 285.
"I didn't play well enough today," said Westwood, getting right to the obvious. "I didn't play badly, but I didn't play great.
"I'm not too disappointed. I don't really get disappointed with golf anymore."
Understandably, the winner gets to feel an opposite emotion.
"This is a day and moment I will cherish forever," Mickelson said.
Poulter's 67 included a mid-round run of eagle-birdie-birdie-birdie. Henrik Stenson of Sweden stayed steady throughout, shot one-under 70 and finished second all alone at even par. No one but Mickelson was able to break par on a course made fast and slick by a week of uncharacteristic warm and dry weather.
Mickelson is 43, the oldest British Open champion since Roberto de Vicenzo won at age 44 in 1967. Ernie Els and Clarke were 42 when they won in 2012 and 2011, respectively. It's the first time the British Open has been won by a player 40 or older three years in a row.
Mickelson concluded his news conference with a statement bearing the perspective of age.
"This is . . . as fulfilling a career accomplishment as I could ever imagine," he said.