Rory McIlroy's quest for a career Grand Slam may have to wait another year after an underwhelming opening day at the Masters, but he says he was encouraged by the way he finished his round.

The 31-year-old Northern Irishman made six bogeys on the first day at Augusta, finishing with a four-over 76, leaving him well off the pace set by Justin Rose with a seven-under 65.

McIlroy's best ever finish at the Masters was fourth in 2015, having won the 2012 and 2014 US PGA Championship, 2011 U.S. Open and 2014 Open Championship.

"My goal is to play well and at least give myself a chance," McIlroy told a news conference after his opening round.

"Honestly I'm quite encouraged with how I hit it on the way in. I hit some loose shots out there, but after hitting the  six iron in the water on 13, I hit some really good shots coming in, so I'm encouraged by that.

"It was just one of those days where I wasn't very efficient with my scoring.

"You're sort of fighting against momentum, but if you make a birdie then you can sort of get going, and [it was] just one of those days.

"But I hung in there, hit some good shots coming in, could have made a couple more birdies, but it's not as if anyone is going really low out there.

"Hopefully feel a little more comfortable tomorrow, go out there and shoot a good one."

There was a bizarre moment for McIlroy when his approach on the seventh hit an onlooker, which was later revealed to be his father, Gerry.

"It was a perfect shot; it was dead straight but I think he was okay," McIlroy said.

"He didn't limp away. He walked away pretty swiftly, so that was all right."

He added: "I knew it was my dad when I was aiming at him."