An upbeat Rory McIlroy believes he will be firmly in contention for Masters glory if he can replicate his day-one performance level for the rest of the week at Augusta.

McIlroy, who would complete a career Grand Slam with a maiden green jacket, shot a three-under 69 to share fourth position at the end of the opening round.

The former world number one trails Jordan Spieth by three strokes and reflected positively on a day that began with a birdie before gains on three of the four par-fives.

"Everything was really solid and if I can continue to play like that over the next three days, I'll be pretty close," McIlroy told reporters.

"I got off to the perfect start, making a three at the first, and I just stayed really patient out there. I didn't try to force things.

"I think anything in the 60s out there today was a pretty good score."

McIlroy and Spieth were among a host of later starters to prosper in benign conditions late on the opening day, with the latter birdieing five holes in succession from the 13th.

"It was out there. I'm not surprised that someone shot that," said McIlroy of Spieth's 66, which means the young Texan has now led after nine of the 17 tournament rounds he has played at Augusta.

"He loves this golf course, plays well around here, he always has.

"He's going to be tough to beat this week."