Graeme McDowell enjoyed returning to the scene of his 2010 US Open victory as he made seven birdies in a 68, although he finished in disappointing style when he three-putted from 20 feet on the final green to sign off with a bogey-six.
A friendly, needling inquisitor also reminded Mickelson that the soft, wet nature of the course made fairways play wider than they typically do at the Monterey Peninsula.
Spieth finished in a tie for 35th place in his last start two weeks ago at the Farmers Insurance Open.
Countryman Scott Langley, starting on the back nine, birdied half his holes on the same course, including one on the par-three ninth, to join Gay at the top of the leaderboard.
Gay finished in the top 10 here past year, too, so he has a little bit of recent history, but he doesn't have a top-20 on the PGA Tour since the Wyndham Championship last August.
The three-time major champion has fallen down the official golf rankings to 21st in the world since his last win, while Spieth has not posted a top-10 finish since the 208 Open Championship.
"I think it's a big factor-you don't know how it's all going to play out, but I think that it's important to get off to a good start", he said.
The fact that it was all turned upside-down and Rollins was hitting golf balls for the first time in more than a week and competing in a PGA TOUR tournament for the first time since last August was as improbable an occurrence as he has ever been part of.
"If you don't score well out here you put yourself kind of behind a bit and it's tough to make up when we got weather coming in because you're trying to force it", Spieth said.
"There's a few things within our family that go back to this place, where my grandfather grew up here", Mickelson said. I don't think it has anything to do with why I've played well here in the past, but you never know. I ran a number of putts by but I made a lot of them coming back and made a lot of short ones. "Crazy. What a roller-coaster day", said Rollins, who at 43 has played in just 24 PGA TOUR tournaments since losing his full exempt status following the 2014 season.