Rory McIlroy has warned Jordan Spieth that 2016 will be a completely different test compared his dominant breakthrough year.
Spieth enjoyed a superb 2015 as he charged to the top of the world rankings thanks to back-to-back major wins at the Masters and U.S. Open, while he was also in contention at The Open and PGA Championship.
His form outshone that of McIlroy, who finished 2014 with two major wins of his own, as the Northern Irishman was unable to replicate that form before an ankle injury hindered his success.
"It will feel completely different for Jordan," McIlroy told The Telegraph. "If you look at the stats at how those who have had a double-major season have performed the next year... well, it's hard to back up.
"It just is. There's so much expectation, so much attention and focus. And I think it is more self-inflicted pressure really as your expectations are so high.
"This time last year mine were through the roof coming off a great season, winning those back-to-back majors and although I started well I never felt I really got into my stride with the injuries and stuff."
McIlroy ended 2015 strongly after returning to full fitness, topping the European Order of Merit, and is looking to continue that form into next year, having undergone laser eye surgery in a bid to boost his chances.
He added: "I've wanted to do this since I was 18, but I wanted to be in position that if anything did go wrong I'd still be OK.
"I've always struggled with my eyes, especially in the summer with hay fever, when you're rubbing our eyes and sometimes things get under the contact lens and so it becomes blurry. But, I mean, it's only been a week since I had it done and it's amazing.
"My vision is so sharp. It has to help putting, help me read the lines on the greens, where there is definitely room for improvement."