Jon Rahm showed Rory McIlroy the way to negotiate the North Course greens at Torrey Pines as he got to within a shot of the halfway lead at the Farmers Insurance Open.
Rahm made a series of early clutch par saves on day two which he insisted were just as valuable as his six birdies in a 67 that boosted his confidence with his new equipment in his bid for a second win at the San Diego venue.
McIlroy was one shot better than his Ryder Cup team-mate over the tougher South Course in the first round, but despite holing a big putt for his second birdie over the first three holes of his second effort, the world No 7 struggled to get the pace of the greens for much of his round.
In contrast, Rahm was dialled in with his new prototype putter and took more of his chances to finish the day just one shot behind 36-hole leader Viktor Hovland.
McIlroy heads into the weekend four off the pace after a disappointing 71, needing a welcome birdie at his final hole on day two to break par.
Rahm, will have a more leisurely Saturday morning preparing for his weekend assault, and he mocked a reporter for asking the Spaniard to assess his confidence levels with his new putter.
"Well, based on my score, I'd say it's pretty good," was Rahm's tongue-in-cheek reply.
The world No 2 was also happy to have played the South Course in far-friendlier conditions in the first round, as day two was hampered by cooler temperatures and the odd hailstorm, with play suspended late in the day due to further adverse weather moving in from the Pacific Ocean.
"Those fairways are narrow enough as it is, and when you start adding the side wind, it's just not fun," Rahm added. "Let's take the first hole today. If you put it in the fairway, in my case today I had 110 yards, just a 'go pin' 100 out of 100 times.
"But if you miss it in the right rough, you have a tree in the way, you can't stop it and you depend on the lie. Things can get complicated and that's on an easy hole.
"If we go to one of those longer ones, like to where you're having a six‑iron into the green and you miss the fairway, you really need to manage.
"The key for me today was some of those early up‑and‑downs. I was able to get some really, really good up‑and‑downs starting on 13. I kept things going and 13, 14 and 18 were really good up‑and‑downs, and we can throw the one on eight there as well.
"I saved four shots right there and was able to finish my first nine holes under par, which was nothing short of a miracle because I didn't strike it well. And then on my second nine, I took advantage of the easier holes, hit it really well and posted a good score.
"I can't really stress how hard it can get. North is easier, South today is brutal, and I mean absolutely brutal. Every shot counts out there.
"Even being on the fairway some shots are not easy and with this wind and rain coming in and out, for those who played the North today, we should be really fortunate to play that course today."