Cameron Smith set a 36-hole St Andrews Open Championship record but predicts a "brutal" test in the third round.
The Australian started Friday three shots back of first-round leader Cameron Young but held the clubhouse lead after reaching 13-under for the tournament thanks to blemish-free second-round 64.
Smith opened with three birdies before adding another trio to go six-under through the first 10 holes.
The Players Championship victor managed pars on his next three holes, before sinking a remarkable long-range putt to eagle the 14th.
Rory McIlroy and Paul Broadhurst's Old Course low-round Open record of 63 appeared in danger, but Smith closed with four pars to finish eight-under for the second round.
Smith still managed to set the 36-hole record at a St Andrews Open, having taken just 131 strokes across his first two rounds, with 132 having been achieved on three occasions before Friday.
While Smith will head into the weekend leading the final major of the year, he expects a tough challenge with a later tee time on Saturday.
"I think being off late again tomorrow afternoon it's obviously going to be a bit firmer, more like the first day, I would say," he told reporters.
"So I would say it's going to be pretty brutal out there. I think there's going to be a few more gnarly pins, and I think being smart is definitely going to be the key to staying at the top of the leaderboard."
Smith remains in search of a major maiden win, with his best finish coming at The Masters in a tie for second in 2020, and believes his patience will again be key with tricky conditions and slow play on the course.
"I think just being patient. I obviously got off to a really hot start and it's very easy to just keep going, getting on the front foot and maybe trying to hit some shots that are a little bit too aggressive," he added.
"But I just stayed patient and holed some really nice putts. I don't think we can really do anything about [the slow play], to be honest, the way the course is set up.
"I'm a really impatient person. Everyone that knows me hates me for it. So I have to try my best out there to be really patient, with the pace of play, and with the golf course as well."
Smith is no stranger to being in contention at a major, having finished in the top five on five occasions across The Masters, U.S. Open, US PGA Championship and The Open.
While appreciating the historic occasion of the 150th Open, Smith insists he will not get caught up in the moment as he prioritises treating every round the same.
"It's obviously a really good spot to be in. I feel like I've been in this spot a lot over the past couple of years, and things just haven't quite gone my way yet," he continued.
"But like I said before, I've just got to be really patient over the weekend. I think the golf course is going to get a lot harder and a lot faster. So just be patient and make good putts.
"I think I've always done a pretty good job of just treating every round the same. I think it's going to be a really cool experience being out there. It has been this whole week.
"But I've always done a really good job of just doing the same thing, going through the same process every morning, making sure I feel the same – get on the range, hit the same shots. It's very boring, but it does the trick."