Jason Day tied for lead despite back

Back pain brought Jason Day to his knees during Thursday's first round of the Masters.

On Friday, Day brought the course to its knees.

He birdied all four of Augusta National's par 5s and finished with a 5-under-par 67 to grab a share of the 36-hole lead.

Photos: Jason Day's Round 2

"I feel very blessed to be able to play, especially over the last two days," said Day, who went down in pain early Thursday before battling through  it for a 70. "Being able to go out there today and shoot 67 was a very, very good score. I can't get ahead of myself. There's still 36 holes left, so the main goal is to get myself into contention and hopefully I can do that by Sunday and if I can do that, maybe capitalize on the opportunities and hopefully grab a green jacket."

If Day can bottle up Friday's round, he'll certainly be in position. The Australian made only one bogey during his round, finding the front bunker on the par-3 No. 12, but followed with birdies on Nos. 13, 15 and 16 and finished with six overall.

He was at his best on the par-5s, with eagle putts on the first three and chipped to three feet on No. 15.

"The whole goal is to try and take advantage of the par 5s here this week," Day said. "The par 3s can be difficult at times and then some of the par 4s you need to get through. But over the last two days, I've played the par 5s nicely. ... If you an get yourself in position and get yourself close to the green or on the green, great. If not and you're out of position, get yourself back into position and wedge it on close and hopefully hole the putt."

At a point on Thursday where, if his back pain had persisted he would have withdrawn, Day now finds himself in position to win his first Masters title.

Photos: 2019 Masters Round 2

"A little bit surprised after what happened yesterday and thinking that, you know, if it doesn't really work out that well with your back then you're obviously disappointed and you're going home early," Day said. "That would be frustrating. ... Today's round, it was just a slow, patient round. I wasn't trying to take anything on too drastically with regards to being too aggressive out there and it just kind of, I had momentum on my side. Just kind of built and built and built."