AUGUSTA, Ga. — Bryson DeChambeau attacked Augusta National in Thursday’s opening round of the Masters — as everyone knew he would — and Augusta National attacked back.

The bulked-up, Paul Bunyan of golf, DeChambeau finished with a 2-under 70 to stand five shots out of the lead held by Paul Casey with 44 players still to complete their first rounds on Friday because of a three-hour weather delay Thursday.

By the time he was finished with his opening round, DeChambeau understood how fortunate he was to walk off the course under par and still in contention.

“This golf course, as much as I’m trying to attack it, it can bite back,’’ a humbled DeChambeau said after his round. “It’s still Augusta National, and it’s the Masters. It’s an amazing test of golf no matter what way you play it.

“I tried to take on some risk today. It didn’t work out as well as I thought it would have, but at the end of the day I’m proud of myself the way I handled myself and finished off — birdieing 8 and 9 [his final two holes] was a testament to my focus level, and wanting to contend here.’’

This Masters always figured to be an adventure for DeChambeau, who’s taken the golf world by storm with his well-documented muscle-weight gain and off-the-charts swing and ball speed.

That adventure was supposed to be about him dismantling Augusta National with his massive length. But the way it began for the Masters favorite, it looked as if he might shoot his way out of the tournament before the weekend.

DeChambeau, who began his first round on the back nine, missed a 5-foot birdie putt on No. 10, then nearly lost a ball on his tee shot on No. 11, having to hit a provisional.

Then he made a mess of the par-5 13th hole, a hole he’d been hitting wedges into the green in two during practice rounds. He blocked his drive into the trees and pine needles to the right of the fairway and then punched his second shot into the bushes over the green. From there, DeChambeau took a penalty drop and fluffed a chip shot.

He walked off the 13th green with a stunning double-bogey 7 to fall to 2-over.

DeChambeau rallied from that with birdies on Nos. 15 and 16 to get back to even par, and he closed his round with birdies on Nos. 8 and 9.

“I’m very happy with the patience I delivered to the course today,’’ DeChambeau said. “I started off strong with a 5-footer and I misread it a little bit, and I just pulled my drive on 11 and went too far and made a great par save. Had an opportunity on 12, lipped it out. And then 13, I just didn’t draw it around the corner enough, and I got greedy.

“I’m fortunate to be 2-under,’’ DeChambeau continued. “I was definitely a little risky out there, and I’m OK with that. Clearly, I didn’t have my best. I just didn’t execute some of the shots I usually do out there. Anybody can win. There’s plenty of guys out there beating me now.

“But to be 2-under for the start of a major championship … always being under par here is great.’’

Much was made about the 47 ½-inch driver he was talking about putting into play this week for added distance. But DeChambeau decided against using it Thursday.

“I don’t feel like I’m 100 percent ready with that yet,’’ he said. “I tried to get it ready for this week, but there was a lot of opportunities that I felt like I could still fly it over bunkers with the 45-inch driver. That’s what I was testing [Wednesday]. Is it really worth it, am I going to gain that much?

“To be honest, as we sat back, we were like, ‘It’s not going to be that much of a gain this week because I am pretty much already flying bunkers out there.’ ’’

Asked how he felt he drove the ball, DeChambeau said, “Not great. Not my best. I got a little, I guess you could say, tight. I wasn’t comfortable with my golf swing. Normally, when I’m really comfortable I can keep going faster and faster, and today I felt like I got a little tighter.’’

With that, DeChambeau headed to the range to work out the kinks for Friday’s second round.