AUGUSTA, Ga. — Gentry Mangun knows what pushes John Peterson’s buttons.

Wednesday night, Mangun told his friend he found a website that predicted Peterson would be one of the most likely Masters participants to miss the cut. When he did, Mangun knew it would put the former LSU Tiger in an attacking frame of mind for Thursday’s first round.

“He loves being doubted, and he loves the big stage,” said Mangun, who is serving as Peterson’s caddy. “The more he’s doubted, the more it focuses him. He’s an unbelievable ball striker, and when he focuses with the intangibles he has he’s hard to beat.”

Peterson didn’t exactly play like a world-beater in Thursday’s first round at Augusta National Golf Club, but he didn’t beat himself, either. Extricating his ball from a string of early hazards, Peterson fashioned a rock steady 1-under par 71 that left him in a respectable tie for 23rd going into Friday’s second round.

And yes, Peterson admitted, what Mangun told him about the website definitely lit a fire under his game.

“I was like, ‘I’m going to free it up and kill it and see where it goes,’ ” Peterson said. “That’s what I did.”

Assigned to the first competitive threesome of the entire tournament, the 2011 NCAA champion admitted he overslept a bit before getting to the course early for his 7 a.m. CDT tee time.

Once he got on the grounds Peterson said there weren’t any nerves, though Mangun said he was anxious Peterson pushed the first shot of his Masters career into the first hole’s cavernous fairway bunker.

But Peterson cleanly clipped a 9-iron onto the middle of the green and made par. He did the same after pushing another drive right into the fairway bunker on the par-5 second hole, and again after dumping his tee shot 30 yards short of the hole into the front right bunker on the demanding 240-yard par-3 fourth.

Peterson then settled down and actually missed several birdie chances as he parred his first 12 holes.

Again going right on 13, Peterson found himself just in the second cut of rough along the edge of the 510-yard par-5’s fairway. With 210 yards to the pin and Rae’s Creek snaking menacingly in front of the green, Peterson launched a 4-iron into the heart of the green and two-putted for his first Masters birdie.

“Unfortunately, we didn’t have any piece of fairway,” Mangun said. “We were dead in it. The thing about Augusta rough is it’s not tall, but it’s very thick. Luckily the wind helped, but when it left the club it looked short.”

Peterson also had 210 yards into the par-5 15th, but easily cleared the large pond fronting the green and two-putted for another birdie.

His only bogey came on the 440-yard par-4 17th. Pulling his tee shot slightly left over the famous Eisenhower tree, Peterson pulled his second shot as well, the ball trundling about 50 feet left of the pin. His first putt rolled 8 feet past and he missed the comebacker to save par.

“It was a stiff breeze,” Peterson said. “I should have backed off and changed clubs, but I didn’t. I got over it and said I would aim right and hook it and I did, but I pull hooked it. That’s a really, really tough putt.

“I’m going to go practice some real hard-breaking 10-footers.”

Most of the patrons arriving at the course early Thursday morning bypassed Peterson’s group as they headed for their favorite viewing spots. His gallery was mostly members of his family, Mangun’s family and Baton Rouge-based fitness professional Kolby Tullier.

Tullier began working with Peterson in October after he shrank to a scrawny 155 pounds and wanted to improve his performance. Peterson has put on 18 muscular pounds since then, improving both his length and flexibility.

Tullier said Peterson has dramatically increased his hip turn from a poor 18 degrees (Tullier said a normal person’s hip turn is about 45 degrees) to about 65 degrees.

“He has to do specific (exercises) before and after the round, plus nutrition. I’m talking to the caddy chasing him up 7 (fairway) doing this,” said Tullier, mimicking eating and drinking motions.

“He’s a great student. He’s been nothing but compliant.”

The mental part of Peterson’s makeup didn’t take much work, Tullier said. He already had it.

“I call him a flatliner,” Tullier said. “There’s no spike in the heart rate. That’s what it’s going to take him to the top. There’s no doubt in my mind. If he continues taking care of his body and trains the way we train, I can see him winning majors.”

Peterson tees off at 9:56 a.m. CDT Friday. Former LSU All-American and 2001 PGA champion David Toms, who shot a 70 Thursday, tees off at 10:29 a.m.

The Masters field will be cut to the low 50 players and anyone within 10 strokes of the lead after Friday’s round.