Adam Scott said he "let a great chance slip" as the opportunity to win the Claret Jug passed him by for the second year running.
The Australian, who blew a four-shot lead with four holes to play in last year's Open Championship at Royal Lytham, was again in pole position after hitting the top of the leaderboard on the back nine.
But, in a repeat of last year, he made four bogeys in a row - this time from 13 to 16 - to knock himself out of the tournament.
Scott, who won this year's Masters to secure a first major title, said: "I let a great chance slip.
"I'm happy I put myself in with a chance and my game's in great shape, that's the good thing to take from it, but I didn't get to the number that Phil finished on.
"Had I played a little more solid in the middle of that back nine, I could have had a chance coming in.
"It will just have to go down in the experience book and something to build on again," added the Australian, who eventually finished tied third, four shots back of winner Mickelson.
Scott now has a win, two second places, a third and two other top 10s from his last 10 major appearances and believes he can add to his Masters victory in the near future.
"I believe I can win another one soon," he said.
"If it wasn't this week, hopefully I'll do the same stuff at the PGA (Championship), and I can put my foot down there on the back nine and run away with it."