Mickelson, a four-time victor of the tournament, ended the day sharing third place at six-under par and just a shot back of the leading duo of fellow Americans Scott Langley and Brian Gay who each shot 64s also at Monterey.
"I have the honour to play all three courses here and, just because of such attractive scenery, I couldn't even focus on where my ball was going", Choi said of Pebble Beach Golf Links, which is set on the famed Monterey Peninsula.
Jordan Spieth plays his second shot on the fourth hole during the second round of the Farmers Insurance Open golf tournament at Torrey Pines Municipal Golf Course - South Course.
And it was also a good day for Mount Juliet's Gavin Moynihan (24), who shot a bogey-free, five-under 67 at the longer but easier Creek Course to share 32nd as Portmarnock amateur Conor Purcell (21) battled back from three-over after nine to post a level par 72. He shot a 2-over 73 at Monterey, which was almost five higher than the scoring average on that track.
NOTES: The 2019 U.S. Open will be conducted at Pebble Beach for the sixth time in June. And I could have really poor years the rest of my career and still have a pretty fantastic career. Dustin Johnson (+500) and Jason Day (+800) are the betting favorites, with Tony Finau (+1800) the only other golfer shorter than 20-1. A sawed off wedge on the iconic seventh hole that scoots all the way back to the pin.
"I'm pleased with it (but) I definitely left some shots out there", said Johnson, four days removed from victory at the European Tour's Saudi International.
"I don't think I've ever done that before, certainly in competition, so that was a big milestone for me".
Hole of the day: After almost dumping his tee shot in the Pacific Ocean, Brandt Snedeker (who has won two of the last six of these tournaments) somehow made birdie from this preposterous position.
What to watch on Day 2: Which of the four superstars at or near the top hangs on at Spyglass? If Day, Spieth, Johnson or Mickelson can somehow get in the house under par on Friday, that player will likely become the favorite to take home the trophy on Sunday.