ATLANTA (AFP) - Rory McIlroy is looking forward to turning the page on a disappointing 2015 after wrapping up his season at the US PGA Tour Championship in Atlanta this week.

The former world No. 1 has endured a mixed season this year, suffering an ankle injury which ruled him out of the Open Championship and failing to add to his haul of four Major titles.

The 26-year-old Northern Irishman said 2015 was a "learning curve" that he would be happy to see the back of.

"It hasn't been the season I hoped for," McIlroy told reporters in Atlanta ahead of Thursday's opening round at East Lake, describing his year as "interesting" and "disappointing."

"Going without a Major, missing arguably the biggest tournament we have - the Open championship at St Andrews, it only comes around every five years - having to sit that one out," McIlroy said.

"There's been a few disappointing moments; there's been a few highs as well. But 2015 won't be a year that I look back on at the end of my career. It was a bit of a learning curve but not one with great success."

Asked what lessons he had learned from the year, McIlroy joked ruefully "Don't play football in the middle of the season! - a reference to the game of football with friends which left him crocked.

"It's just been a difficult year. Humbling if nothing else," he added.

McIlroy has been succeeded at various times by both Jordan Spieth and Australia's Jason Day as world No. 1.

But while McIlroy believes that on current form Day is the best player in the world and deserves his world No. 1 ranking, Spieth has been the player of 2015 by virtue of his wins at the Masters and US Open.

"Two Majors trumps all else," McIlroy said.

"There's obviously a ballot at the end of the year and I know who I'd be voting for.

"That's no disrespect to Jason at all - he's done great, he's been the best player for the last three months - but I feel like you've got to go on Majors and Jordan has been the best player in those tournaments this year."