Winning the U.S. Open last year didn't just earn Rory McIlroy his first major title, it made him believe he was ready to become the best player in the world.
McIlroy justified his long-held reputation as golf's new star and possible heir to Tiger Woods by rolling to an eight-shot victory at Congressional last June.
Since then he has topped the rankings, overtaken Luke Donald and Lee Westwood, and the 23-year-old Northern Irishman believes there is no reason he can't stay there.
"I think maybe after Congressional last year, I started thinking of myself as definitely one of the elite players," McIlroy said.
"You have to believe that you're the best and I certainly do believe that. And it's just a matter of going out there and showing everyone what I believe."
What McIlroy has done since his record-breaking exploits at Congressional is plant some consistency into his game, putting himself on a par with Donald in that regard.
From the European Masters last September through to his most recent win, at the Honda Classic at the start of March which lifted him to No. 1, McIlroy chalked up two victories, eight top-five finishes and an 11th place. His missed cut at The Players Championship two weeks ago was the first time he failed to make the weekend in 23 tournaments.
No wonder he is so bullish.
"I think you have to believe that you're better than anyone else," he said. "On my day, I believe I can beat anyone in the world - it's just finding that capability of when you're not playing the best, to still come out on top.
"That's the thing that I'm trying to learn how to do, because I've proved in the past that when I'm on my game, I'm pretty hard to beat."
His comments contrasted sharply to those of Donald, when asked if he was the best player in the world. Unlike McIlroy, Donald took the diplomatic route.
"I don't really think in terms of that. I think my focus is to try and always continue to improve and be a better golfer," Donald said.
Donald described McIlroy as "the most naturally gifted player there is."
"He just has that look about him - free-flowing, hits the ball far, just seems really effortless," the Englishman said. "I feel, personally, if I don't work hard and grind it out, I'm not going to be that successful. It's just not that easy for me."
This week's BMW PGA Championship at Wentworth will be McIlroy's first appearance at a European event in seven months, since the Dunhill Links Championship in Scotland last October.
Now based in the United States, he has limited his trips back over the Atlantic but always relishes a return to the home of European golf, which he visited regularly as a kid when the World Match Play Championship was hosted at Wentworth.
"This is a golf course I love, a golf course I came to every year since I was 10 years old," McIlroy recalled.
"I ran 36 holes every day. My mum and dad left me at the first tee at 8 a.m. and I didn't see them until 6 p.m. It was great."
McIlroy plays alongside Ernie Els and Martin Laird for his first two rounds at an event where he has only one top-10 finish in four starts.