Mickelson's three shot victory over Henrik Stenson and four shots over Ian Poulter, Adam Scott and Lee Westwood left little doubt as to where he stands amongst the game's greatest and as a result of his victory he has moved to the number two position in the world.
With four major championships to his name prior to this week, Mickelson was already considered one of the game's most successful players but if he was to elevate his status in the game to greatness he needed to prove to himself and others that he was not a one trick pony capable only of winning in the US.
The last two weeks have well and truly dispelled that perhaps unwarranted theory although even Mickelson himself admitted that he had been unsure of his capacity of winning in the sort of conditions Open Championships present.
His victory last week in Scotland and now this have turned him into the complete golfer and there seems little doubt that even at the age of 42 there is more to come. If he was to go on and become the oldest golfer to win a major championship then few would now be surprised.
Given Mickelson's drive to continually perfect his game then there seems little doubt that more majors will come his way and when taking into account the personal issues he has faced away from the golf course with the battle against breast cancer his wife Amy has endured and come through then it makes his achievements even more meritorious.
It may be that his devotion to family played a part in this victory as two weeks ago he missed the cut at the Greenbrier tournament where he had taken his family to enjoy the fun facilities at White Sulphur Springs. He left for Scotland with the family in what appeared to be a relaxed state of mind.
In the lead -up to the Scottish Open Mickelson said; "I think that the last eight or nine years, I've started to play better golf in links style, better golf in bad weather, better golf along the ground and I've gotten a lot better. But it is still a challenge for me and it's still not something that I grew up doing and it's still something that I'm trying to learn as I continue through my career. So I'm always cautiously optimistic.
"The British Open, The Open Championship, it's one of my favourite events because it's one of the most challenging events for me. I'll have to get my game sharp and one of the things I've learned over the years, especially at Muirfield; that you need an element of luck relative to tee times and you need a bit of a break there, as well."
Sure there was an element of luck this week as there always is when winning a tournament but there was a lot more class and skill as his final round of 66, the equal best of the week on an increasingly demanding layout, proved.
Mickelson and the runner-up this week may well start a flood of golfers heading for the Scottish Open as their lead-in event as Mickleson's win at Castle Stuart and Stenson's 3rd place finish tell the story of that venue being perfect as a place to prepare well.
Mickelson began the final round four shots behind Lee Westwood and although he made an impressive start with an outward nine of two under 34 he was still two behind Westwood who was playing 40 minutes behind him.
At about that same time Australian Adam Scott began a run of four birdies in five holes to move to two under and when he produced the fourth of those birdies he was at 2 under and had the lead.
Two holes later however would come a stretch of four consecutive bogeys that destroyed any chance of redemption for a similar run twelve months ago. This time however it might be that it was not a case of handing Mickelson the victory but the American winning it off his own bat.
Mickelson birdied four of the last six holes and while his lead looked a formidable one even before his birdie at the last, the 12 foot putt there all but sealed the deal.
Westwood and Stenson by then were his only genuine threats and in order to do so they would need to birdie their final three holes which in a PGA Tour event on a pristine layout in the US might have been achievable but on the demanding finishing stretch at Muirfield it was all but impossible.
So it was to prove and instead of closing the gap Westwood extended it when he bogeyed the 16th. Although Stenson kept some hopes alive when he birdied the 17th the miracle shot at the last was a bridge too far and he finished two shots behind but recorded his best ever Open finish.
Mickelson was emotional when speaking to the media after his round. "This is just an amazing feeling to win this great championship and to play probably the best round of my career.
"I hit some of the best shots I have ever hit, putted better than I have ever putted and you know I was getting ready to play earlier and I thought I needed to bring my 'A' game today and I needed to show up and play some of my best golf and I did. I played some of the best golf of my career.
"To make it even more special was to have my family here, Amy, Amanda, Sophia and Evan here and Bones (caddie), Steven Roy and Butch Harmon it is really special."
So what was the turning point in the round today where he felt that he had a genuine chance?
"I was behind most of the day until I got to the 13th and I hit a really good 5 iron in there and it was a putt that was going to make the rest of the round go one way or the other. I thought if I could make it and get some momentum and get to even par for the championship it was a score that I thought had a good chance and when it went in it gave me a nice momentum boost .
"When I was walking up the 17th that was the moment when I had to compose myself because I hit two of the best three woods ever and that is the exact reason why I don't have a driver in the bag as those two three woods were the best shots of the week to get it on that green.
"When I was walking up to the green I realised that this was my championship and that I had it in my control and I was getting a little emotional and had to slow down and regain my composure as I still had to make a two putt birdie and make tough par up the last."
"Being so down after the US Open to come back and use it as motivation and to turn that emotion around in a month feels great."
Despite his amazing record Mickelson understands he still needs to win a US Open to be considered one of the game's greats. "I think if I am able to win the US Open and complete the career Grand Slam then I think that is the sign of the complete great player and I am a leg away. I think there are five players to have done that and I think those players are the greats of the game."
Mickelson may well deserve the 'great' tag already but he would dearly love to win his national open after six runner-up finishes.
Early leader Zach Johnson finished in a tie for 6th with Hideki Matsuyama and Tiger Woods, Woods battling from the get-go when he three putted his first hole for bogey. When Woods birdied the 14th he was not yet out of it but when he bogeyed the 15th he was.
A special mention should be made of Matsuyama's great week. A month after finishing 10th on debut at the US Open, the 21 year old Japanese star has finished 6th on debut at the Open Championship. Matsuyama has now made the cut in all four major championships he has played leading the Amateurs on debut at Augusta National and making the cut the second year there and now finishing 10th and 6th at his two majors as a professional.
If ever there was a Japanese golfer capable of winning a major he is it.
Of the Australians other then Scott Jason Day fell away over the final day for a round of 77 and 32nd position, Geoff Ogilvy was 44th, Marcus Fraser 54th and Peter Senior 79th.