Dustin Johnson and Justin Thomas eye second major wins at Masters - in pictures

Players are having to adapt to an autumn action after tournament was delayed by Covid-19

World No 1 Dustin Johnson and third-ranked Justin Thomas believe it will take an unusual approach to win the Masters with some aggressive tactics.

The American duo shared the clubhouse lead on nine-under par 135 with Australian Cameron Smith and Mexico's Abraham Ancer in the second round with 48 golfers still to finish on Saturday.

Each player hopes to win the green jacket symbolic of Masters supremacy for a second major crown, Johnson after his 2016 US Open title and Thomas after his 2017 PGA Championship victory.

Thomas has watched shots do unexpected things this week, a mix of rain-softened conditions and autumn weather requiring some adaptation from lessons learned over time at Augusta National.

"It's a lot softer and a lot more scorable, but it really has just come down to executing a little bit better and minimizing the mistakes," Thomas said.

"You really throw all past knowledge out the window, as weird as that is.

"It's not like I'm the only one that has to adjust or may be uncomfortable in certain situations. The entire field is dealing with the same thing."

Johnson, trying to become the first top-ranked Masters winner since Tiger Woods in 2002, is happy with his shot making but figures he must keep an attacking mindset even as the course becomes firmer after showers early in the week.

"We're still going to have to go out," Johnson said. "It's going to be soft enough to where you're going to have to attack the course and play aggressive and keep swinging like I am.

"I like where I'm at. I like my position heading into the weekend."

Thomas has gotten better results every year in his four Masters starts, placing 12th last year, and he feels like he has left shots on the course.

"It's definitely not as low as I feel like I could or should be, but we're in good position going into the weekend," he said. "I know the subtle nuances. I just simply haven't executed it and performed it well."

Johnson, the PGA Player of the Year after winning the Tour Championship, has been runner-up in three of the past six majors and will focus on the par-5 holes, hoping his long-driving game helps make the difference.

"Need to play the par-5s a little bit better over the weekend. That's the only thing that I need to really do any better," he said.

Thursday's overnight leader Paul Casey will be one of those heading out on Saturday morning in Augusta. He had one bogey and 10 pars in the 11 holes he managed on Friday.

Defending champion Woods was level after 10 holes to remain at four under par.

Pre-tournament favourite Bryson DeChambeau's four birdies were offset by four bogeys and a triple-bogey seven at the third after he lost his ball.

It leaves the US Open champion one over with six to play and battling to make the cut.