If Woods wants to capture his fifth career PGA Championship title and 16th major overall, he'll need his best game to show up, and for his aching back to hold up under the pressure.
"This is a big run for us coming up here. I've been gearing up for this, and looking forward to the challenges of not only this week, but obviously the playoffs and a US Open and then the Masters," Woods said on Tuesday.
Northern Ireland's McIlroy is one of several players who have held the world number one ranking at some point this season.
He has already won two PGA Championships, but his last one in 2014 also accounts for his last major title.
Rahm, Phil Mickelson and Sergio Garcia make up another marquee opening round grouping.
Rahm is coming off a recent victory at the Memorial Tournament and is trying to deliver on the big stage by claiming his first major championship.
"Hopefully I have it in me," Rahm said on Tuesday. "Hopefully I've done the right things. Physically I feel great and mentally I feel like I'm great. I'm ready."
Three-time major champion Jordan Spieth needs to win the PGA to complete a career Grand Slam. With that he would join Gene Sarazen, Ben Hogan, Jack Nicklaus, Gary Player and Woods as the only players who have won each of the four majors.
"It's something that I really want," said Spieth, 27. "It's probably the No. 1 goal in the game of golf for me right now. I'd love to be able to hold all four trophies."