AUGUSTA, Ga. (AP) — As Rory McIlroy was warming up on the practice range Thursday morning, Jack Nicklaus was busy touting the Northern Irishman’s game by saying he had a “very, very good chance” to repeat as Masters champion.

McIlroy spent the rest of the day proving him right.

The 36-year-old McIlroy opened his title defense with a 5-under 67 to claim a share of the early lead with Sam Burns at Augusta National and position himself for a run at becoming only the fourth player to win back-to-back Masters.

“Rory’s got the monkey off his back, and I think he has a very, very good chance to repeat,” Nicklaus said early Thursday after serving as the Masters' honorary starter.

After years of heartbreak and close calls at Augusta National, McIlroy beat Justin Rose in a playoff last April to complete the career Grand Slam in his 17th Masters start.

So the pressure to win wasn't hanging over his head on Thursday.

“I know that I can go to the Champions Locker Room and put my green jacket on and have a Coke Zero at the end of the day,” McIlroy said.

McIlroy said last year's win allowed him to fully commit to his shots Thursday and make good swings without necessarily worrying about where the ball went.

He found there is a certain freedom in that approach.

That said, it wasn't as if he wasn't nervous when he stepped onto the first tee for the year's first major championship.

After all, he said, “It’s the Masters.”

“If I felt absolutely nothing on that first tee, that’s not a good sign,” McIlroy said. “So it was nice to feel my hand shaking a little bit when the tee went into the ground and struggle to put the ball on top of the tee. I knew I was feeling it. That’s a good thing.”

He shot 34 on the front nine despite struggling to find the fairways early, and then willed his way to a birdie on the par-5 13th hole.

After his tee shot sailed right and well into the pine straw, McIlroy spent more than 10 minutes trying to clear patrons out of his way before delivering a perfectly placed punch-out between the tall pines into the middle of the fairway.

He followed with a pitching wedge just past the hole and then rolled in a downhill putt for a birdie. Two more birdies followed on Nos. 14 and 15, moving him into a tie atop the leaderboard.

He finished with six birdies and made his only bogey on the par-4 third hole.

“I still have high expectations of myself, but my expectations are more, did I make good decisions today? Was I committed? Was I trusting?” McIlroy said. “It wasn’t my expectations of I’m going to go out and shoot 65 and did I do it?”

In other words, just focusing on the shot at hand and letting the chips fall where they may.

Nicklaus was the first to repeat at the Masters, winning in 1965 and 1966. Nick Faldo (1989-90) and Tiger Woods (2001-02) matched his feat, but nobody has been able to repeat since.

Nicklaus knows repeating is not easy.

He broke the Masters scoring record with a 17-under 271 in 1965, then returned the following year to play Augusta National in much tougher conditions. He finished 17 shots worse at even-par 288, but still won in a playoff.

“I think winning a Masters makes it easier to win your second one,” McIlroy said.