"Does it add to anything? Honestly at a World Golf Championship, we prepare for these and we think of these as a step below a major championship, that's how we feel," Spieth told reporters at the Trump National Doral Resort on Wednesday.
"Everyone is fighting for the same prize and when we get out there we are playing our own game. I'm not trying to down play it and for me personally, I would say, 'Sure, it's going to be a lot fun because I enjoy playing with both of them.'
"But I don't think anyone is buying into the 'Big Three' because I don't think that's a necessary comparison when you look at the 'Big Three' from the past," said Spieth, referring to golfing greats Jack Nicklaus, Arnold Palmer and Gary Player.
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This will be only the second time that Spieth, Day and McIlroy have been grouped together on the PGA Tour, and McIlroy was looking forward to the prospect as he prepared for Thursday's opening round.
"It is going to be fun," said the 26-year-old. "I have played a lot with Jason and a lot with Jordan over the past few years but we haven't really played together in a three-ball.
"So the next two days are going to be enjoyable and it will be good out there, hopefully a little bit of a buzz around that group."
Both Spieth and McIlroy will tee off on Thursday on the challenging Blue Monster layout after missing the cut in their most recent PGA Tour starts.
Masters and U.S. Open champion Spieth failed to advance at the Northern Trust Open in Los Angeles two weeks ago while McIlroy struggled with his putting on the way to an early exit at the Honda Classic last week.
"I will try and gain some momentum back off of Los Angeles, that was a bummer," said the 22-year-old Spieth. "I've been working pretty hard on my game for the last week-and-a-half to try and get it ready for a challenging golf course.
"Only the scores will end up telling but I feel a little bit better, I feel better about my game."
Twenty-nine of the world's top 30 players are competing this week at Doral in the first of the season's four elite World Golf Championships events. American Dustin Johnson defends the title he clinched by one shot last year.
(Reporting by Mark Lamport-Stokes in Los Angeles; Editing by Frank Pingue)
