Justin Thomas said you have to “throw all past knowledge out the window this week” as the American star eyes his first Masters title.

Thomas, world number one Dustin Johnson, Masters debutant Abraham Ancer and Australian Cameron Smith are all nine under through 36 holes at Augusta.

Former world number one Thomas claimed the 2017 US PGA Championship, though he has never won the Masters – last year’s 12th-place finish his best performance to date.

Thomas has improved in every Masters appearance since 2016, but the 2020 edition is like no other after the iconic major was rescheduled from its original April start to November in Georgia amid the coronavirus pandemic.

After carding a second-round 69, Thomas told reporters: “I know the golf course, I know what to do, what not to do. I know the subtle nuances. I just simply haven’t executed it and performed it well. 

“You have to really throw all past knowledge out the window this week, as weird as it is. I had a chip on 15 this morning to that front pin that usually would be just brutal and really, really hard to hit close, and I had to trust that I just kind of had to gas it and hit it pretty hard and it was going to spin. Balls are making pitchmarks with chip shots and pitch shots. 

“A lot of the history and things that you know about the golf course, it can sometimes hurt you this week because of what you’re used to. But at the end of the day, it is a lot softer and a lot more scorable, obviously, but it really has just come down to executing a little bit better and minimising the mistakes.”

Asked how difficult it is to throw away that past history and knowledge and trust the now and new conditions, Thomas said: “It’s really hard… it is weird, but everyone’s dealing with it. It’s not like I’m the only one that has to adjust or make or may be uncomfortable in certain situations. The entire field is dealing with the same thing.”

Ancer enjoyed a fine second round, the Mexican signing for a five-under-par 67 to earn a share of the overnight lead.

He is trying to become the second Mexican player to win in as many weeks on the PGA Tour, after Carlos Ortiz claimed last week’s Houston Open.

Asked about his Masters invitation, Ancer said: “It was awesome. I actually have it framed in my house, so it’s right there in my living room, and it’s something that I dreamt since I was a little kid to play here. I was really, really excited to be here my first time ever, I’ve never been to the tournament or watched, anything, was last week. I played with a member, Nick Evans, awesome, I couldn’t have picked a better guy well, I’m lucky he picked me, I guess. I didn’t pick anybody. 

“It’s been amazing, and I know maybe it’s not the same as in April, but I mean, it’s incredible and I love it out here, I love the golf course, and I think this is probably one of my favourite places in the world.”

Smith (68) added: “It’s obviously good to be in contention on a weekend, and I feel like I’ve been there enough where I can have a good crack at it.”