Shrugging off intermittent rain, the five-times major champion finished strongly with four birdies in his final six holes to post a six-under 138 halfway total on a day when half the field did not complete the round due to a morning weather delay.
American Scott Piercy led at 14-under after 12 holes when play was halted, while American Bill Haas (70) was the clubhouse leader at eight-under 136.
“Given the conditions, this was some of the best iron play I have ever had,” Mickelson told Golf Channel.
“(I was pleased) to get the distance control right, the trajectory and spin right on spongy greens, and give myself as many birdie opportunities as I had.
“I hit a few wild ones as well. I guess it’s just my normal game.
“I certainly didn’t drive it the way I need to, but that’s my game. I’m not the most accurate guy but put an iron in my hand and I can make some birdies.”
One of the wild ones was the tee shot at the par-three seventh, which he sprayed into a beer stand selling one of Europe’s most famous lagers.
Mickelson, given a free drop, hit a 'Stella' pitch shot from hard-packed mud, only to miss the subsequent par-saving putt.
Asked whether he had considered picking up a beer while passing the stand, the quick-witted Mickelson replied: “No, I picked up a bogey is what I picked up. It sucked.”
Haas, meanwhile, moved into a position to possibly continue his family success, after his father Jay at age 62 won an event on the 50-and-over Champions Tour on Sunday.
“It was awesome to watch, made me proud,” said 34-year-old Bill. “It doesn’t help me make any more putts out there but it would be nice to have a good finish.”
Leader Piercy, boosted by a pitch-in eagle from 40 yards at the par-five ninth, moved two shots clear of fellow American Johnson Wagner (14 holes) before play was suspended for the day.
The second round will resume at the crack of dawn on Saturday, with the third round scheduled to start around noon.
(Reporting by Andrew Both in Cary, North Carolina; Editing by Ian Ransom)
