It never got much worse, but DiMarco already had done his part.
He made seven birdies in his round of 6-under 65, giving him a fleeting chance in another major championship. Sergio Garcia didn't budge in the light afternoon rain, leaving DiMarco six shots behind.
But it at least gave DiMarco hope, if not for Sunday, than the rest of the season.
'This is a really good step in the right direction here, for three days to put myself in position,' DiMarco said.
DiMarco has been a forgotten figure since he finished two shots behind Tiger Woods last year, his third runner-up in a major.
But that was his last top 10 on the PGA TOUR, an ugly stretch of 26 tournaments. Having gone six straight years inside the top 20 on the PGA TOUR money list, DiMarco is at No. 119 in the tour's new FedExCup point list.
'Everybody is more concerned about me than me,' DiMarco said. 'I feel fine. It wears on you when everybody goes, 'What's up? Everything good?' After a while you go, 'Maybe there is something wrong with me.' Obviously, I haven't had as great a year as I'd like to.'
Physically, he hasn't been at his best.
There was an injury last year when he slipped during a ski vacation, and a flask in his back pack jabbed him in the ribs. He has taken a cortisone shot for his left shoulder, which might need surgery at one point.
'My year has been weird,' DiMarco said. 'I've been playing really solid, I just haven't been putting it together.'
Perhaps the biggest change might be his caddie.
DiMarco replaced longtime looper Pat O'Brian at the British Open last year, going with his brother-in-law, Ryan Rue. The other caddies called him 'New Guy,' which turned out to be appropriate. DiMarco said it was like starting over.
'I went to a guy I had to teach everything to,' he said. 'To be honest, it got to be a burden. I don't have to do that with Pat. He knows his job, he knows what he's doing. And we go out there and we play golf, and we're a really good team. I've had a lot of guys come up to me and say, 'What took so long?' They could see it.'
Why get rid of O'Brian in the first place?
DiMarco said he was struggling coming into the British Open last year and tried to shake things up. It didn't work.
But he found his stride on Saturday, opening with three birdies in the first six holes, getting his name on the leaderboard with a 12-foot birdie on the 11th that had him pumping his fist as he walked to the cup to retrieve it.
And while he missed a 4-foot par putt on the 16th, the former Florida Gator finished strong with a birdie on the 17th and a birdie putt on the 18th that stopped inches from going in.
He still has a lot of ground to make up, but DiMarco at least will be in the second-to-last group. He'll be in the mix, foreign territory for him over the last few years.
'I'm going to go out aggressive, play the course like I've been playing the course,' DiMarco said. 'There's holes you can be aggressive on and holes you don't want to, and that's all I'm trying to do tomorrow.'
The timing could not have been better.
DiMarco currently is not eligible for any of the majors next year. And the guy who made the winning putt for captain Jack Nicklaus in the Presidents Cup two years ago didn't figure to be part of this year's team.
'The Presidents Cup is obviously very important to me,' DiMarco said. 'If I played good and solid ... I didn't feel like I needed to get into the top 10, basically. But I felt like as long as I showed them I had a heartbeat and I could get back in the top 15 or around 15, that I probably would have a pretty good chance of being selected.
'This is a big step toward that.'