Make no mistake: Rory McIlroy is still the game's No. 1...but Jordan Spieth has done everything to remain the flavor of the month.

Spieth, 21, became the youngest U.S. Open winner since Bobby Jones in 1923, and like McIlroy, has won two majors since last year's U.S. Open at Pinehurst. On track to complete the single season Grand Slam, Spieth is mounting pressure on his closest rival, something 2014 European Ryder Cup captain Paul McGinley readily admits.

"When someone wins their first Major like Jordan did, you expect added pressure and expectation put on their shoulders, but [Spieth] just went and won the next one," McGinley said (via Belfast Telegraph). "He's got something special."

"Rory's now got to step up to the plate. As commendable as his performance was on Sunday and again during the final round of The Masters, the bottom line is he's had too much ground to make up in both tournaments," he added. "He's made the mistake of getting off to slow starts in each of the last two Majors and Jordan has gone on to win both of them."

"He's putting it up to Rory, which can only be a good thing."

McIlroy remains undeterred. The 26-year-old is confident in his abilities.

"If you look back at the last four or five years, I've won more Majors than anyone else in that time period," McIlroy said. "So, do I feel like the best player in the world? Yes. And obviously I want to go out every week and try to back that up and show that."

Despite not winning any Majors, McIlroy has two Tour victories and six top-10 finishes this year.