He made a decision to put in a new 4-iron, which he used to hit his second shot into 18 feet for eagle on the par-5 sixth.
The Portrush native (39) hit just seven fairways in a three-over 75 while Lowry's second round was undone by a costly triple bogey at the third (his 12th) and shot a 79 to finish on seven-over.
But rather than take a free drop in the rough, and behind a tree, Snedeker managed to clip a superb wedge over the seats and onto the green, 20 feet beyond the pin, although he was unable to make the par putt. So I ended up coming down here and seeing a physio and trying to do as much work as I possibly could to get ready for this week. "To win an event that has the name of one of the greatest players on earth would be really special, but it's only Thursday". (It also says the "average" golfer has a 12,000-to-1 shot at making an ace).
The defending champion got off to a sluggish start in Orlando, sandwiching a birdie at the 13th (his fourth) between bogeys at the 11th and 18th. This time, the new Rules of Golf helped Mickelson because he was able to move the ball one club length and escaped with double bogey.
The double-bogey included a weird attempted recovery shot, with the left-handed Mickelson switching to a right-handed stance in a failed attempt to play his way out of trouble when his tee-shot ended up nestled against a fence alongside the left fairway.
Rory McIlroy of Northern Ireland looks on from the 15th tee during the second round of the Arnold Palmer Invitational.
Justin Rose, who has a chance to return to No. 1 in the world this week, opened with a 71.
The 31-year-old walked off the course after playing his second shot on the 16th after teeing off on the back nine.
Meanwhile, Aaron Baddeley is the only other Australian in the field at the prestigious Palmer invitational after 2016 champion Jason Day withdrew mid-round on Thursday with a back injury.
Quizzed by reporters after the round Day, who didn't play a practise round or the pro-am this week, said he had hoped the injury would settle down during the round but it hadn't.
"I (aggravated) it last Sunday and then got an MRI Monday, which came back that I had an annular tear in my disc, and then I've got facet problems as well", Day told PGATour.com.