The best part of his round was a series of pars when Mickelson said his game went through some "technical difficulties."
Once he got that sorted out, he made birdies on the 14th and 15th holes, and even a bogey on the 18th didn't spoil his day too much. It was his lowest start at the British Open since a 69 at Hoylake in 2006.
"I love the fact that I shot under par because it's a very challenging course out there," Mickelson said.
Mickelson had his record sixth runner-up finish at the U.S. Open at Merion, where he started the final round with the lead. He made two bogeys with wedge in his hand on the back nine, but he was particularly bothered by the par-3 third hole.
Walking off the fourth tee, he looked back at Davis and said, "That's terrible - 274 yards? You can't even reach it," Mickelson said.
As for the R&A and the pin placements on some of the holes at Muirfield?
"Well, hopefully they'll ... let go of their ego and set it up reasonable, but you just never know," he said. "I think both the players and the tournament committee were excited about the conditions because of how firm the golf course is playing. And I think they wanted a little bit more wind, but there's enough wind that it's challenging to maneuver shots. You have to hit shots to accommodate the wind, to get the ball coming into the greens at the right angles and stuff."