Day (71) climbed as high as a tie for second place, just one shot behind the Grand Slam winner, midway through the second nine of Round 2.

He now needs something extraordinary to happen over the weekend after a combination of a bogey on the final hole by the Queenslander and an incredible run of six birdies in his last seven holes from the Northern Irishman opened up an eight-shot difference.

Playing for the first time without the pressure of trying to win his first green jacket, McIlroy threatens to run away with back-to-back Masters and a sixth major championship after his brilliant 7-under-par 65.

He sits at 12-under-par, with his birdie on the final hole setting up the largest 36-hole lead in Masters history, six shots over Americans Patrick Reed (69) and Sam Burns (71).

Day is in a group tied for seventh at 4-under-par, possibly too far back already, even though there are still 36 holes to play.

“I think if I can just keep myself within arm's length of the lead, just never know what happens out here at Augusta, especially on the weekend,” the former US PGA champion said post-round while the margin was a little more manageable.

“But more so on Sunday. Things can happen and turn pretty quick on a dime, just with how scorable some of the holes can be, and obviously, with the dramatic finish we have typically.

“I'm just going to go under the radar and do my thing. I felt like it's been a pretty good formula so far over the last few days, what I've done.”

Day has been preaching patience, and it has served him well, steering him to 25 holes without a bogey until a misstep at the 11th, where he failed to get up and down from just to the right of the green.

Another bogey followed on 18, a tricky downhill eight-footer for par, scraping the edge of the cup after his tee shot found the trees.

The only other Australian to make the halfway cut, for the 22nd time in 25 appearances at Augusta National, was Adam Scott (74), who is at 2-over, a massive 14 shots behind McIlroy.

The run of missed cuts in major championships continued for Cam Smith (77), who finished at 7-over, three more than the mark required, while Min Woo Lee (77) was a distant 11-over.

Scott looked like he could be a contender when he was only four shots behind the lead around lunchtime in Georgia.

But he dropped three shots over the closing two holes, a three-putt bogey from long range at the par-3 16th and a double-bogey six at the closing hole when his tee shot saw his ball dive into the trees to the left, leading to a penalty drop.

“It's fine lines out here,” he said.

“I made a bad swing off 18 tee, and it cost me a couple, and now it's making it hard for me to see how I work my way back right into it.”

Cam Smith’s chances of contending slid away early on day two when he bogeyed three of his first five holes, leaving him scrambling to make his first major cut since the 2024 US Open.

All hope of making the weekend disappeared when he found the water on the par-3 16th, leading to a double-bogey.

After a 78 on Thursday, Min Woo Lee was having a much better Friday, even-par for his second round before a disastrous four-hole stretch ruined any chance the Australian No.1 had of playing at the weekend.

A horrible downhill lie in a back bunker at the 12th created a double-bogey, and Lee then found the water on the two par-5s, making six on both, adding to a bogey on the par-4 14th.

The world No.25, who said his preparation was “unbelievable”, finished with just two birdies for his 36 holes – one in each round.

“Pretty disappointed. Making two birdies out here is not going to cut it. Didn't have my best at all,” Lee said.

“I felt like I had five birdie chances throughout 36 holes, which is not that good.”

The poor performance comes as a huge surprise after Lee’s great start to the PGA TOUR season and preparation for Augusta that he described as “unbelievable”.

“You would think I would be winning the tournament the way I was leading up to the event,” he said.

Jason Day leads the Aussie charge. PHOTO: Getty Images.

Trying to become just the fourth player to win the Masters in consecutive years, McIlroy’s Friday highlights show included a tee shot that slid down the slope to inside a metre on the par-3 16th and a chip-in from distance a hole later.

Among the other notables to miss the halfway cut were Ryan Fox (5-over), Bryson DeChambeau (6-over), and Australian Open winner Rasmus Neergard-Petersen and Scotland’s Robert McIntyre at 7-over-par.