Woods, who is set to make his PGA Tour return at the Hero World Challenge in December, has won more WGC events than any other golfer in history.
With 18 wins in these competitions, he has 15 more than the next closest (Dustin Johnson and Geoff Ogilvy have three).
McIlroy was asked why Woods found so much success in these events and he did not hold back.
"Honestly I think because of the no-cut format," McIlroy said. "I think that's probably a big thing to do with it. You play with a little more freedom.
"And I never want to criticise Tiger's game at all, but if there was one thing or one negative you would say about him was that he probably wasn't the fastest starter in the world in normal golf tournaments. So here, you don't really have that pressure of trying to play your way into a tournament.
"It's a four-round tournament. You know you're getting four rounds, so you've got plenty of time to make birdies and play well. And I think just from the get-go, you don't quite feel the pressure. Even though you shouldn't really be thinking about the cut or anything like that, but it is a little bit of a mental thing. But it takes the weight off you, and you can go and play just that little bit freer."
After his honest assessment, McIlroy ended his answer with the reason everyone else was thinking.
He said: "Can I just add one more thing to why he won so many? Because he was the best. There's another reason."
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