St. Louis - Tiger Woods and Rory McIlroy, past major winners trying to rise once more from contenders to champions, tee off side-by-side when the 100th PGA Championship starts on Thursday. 

Woods, eight months into a comeback from spinal fusion surgery, and McIlroy, seeking his first major win since the 2014 PGA, will be joined by defending champion Justin Thomas for the first two days over the 7,316-yard, par-70 Bellerive Country Club layout. 

"You certainly get thrown at the deep end straight away in a group like that," McIlroy said. "I guess it focuses you straight away. It's going to be a big atmosphere out there and I'm looking forward to that." 

That trio and top-ranked Dustin Johnson are odds makers favourites for the year's last major event on a rain-softened course where length will help but second shots into tight landing areas will be critical. 

"It's advantageous for the guys who hit the ball in the air and can carry it a long way. I just need to be able to do that," Woods said. 

"If you're able to hit the ball well and put the ball in the right sections, you'll see a bunch of birdies. If you don't, you'll see the field get separated pretty quickly." 

Woods, a 14-time major champion, has not won a major since the 2008 US Open and hasn't won any event since the 2013 Bridgestone Invitational. But he fired his lowest final round in five years to take fourth in June at the PGA National and led in the British Open final round before sharing sixth at Carnoustie. 

"He had to learn how to move again. He had to learn how to swing. I mean, 18 months ago the guy couldn't walk," McIlroy said. "To get to this point is a phenomenal achievement already. 

"If he could go ahead and win another major with his fifth golf swing, I mean, that's unbelievable." 

Fifth-ranked McIlroy has five top-10 showings in the past nine majors, sharing second at last month's British Open and fifth at the Masters. 

"The only thing I haven't done is win enough," McIlroy said. "I've given myself a lot of chances. I played in a lot of final groups and I haven't played well enough when it has counted." 

Three-time major winner Jordan Spieth will make his second try at completing a Career Grand Slam after sharing 28th last year at Quail Hollow. He would join Woods, Jack Nicklaus, Gary Player, Ben Hogan and Gene Sarazen in the feat with a victory. 

"It will always be circled to complete the career Grand Slam, which will ultimately achieve a life-long goal for me, so certainly emphasis in my head on it, but nothing overpowering," Spieth said. 

Eighth-ranked Spieth could become the first to finish the Career Slam at a PGA and do it on the same course where South Africa's Player did by winning the 1965 US Open. 

"It's a great position to be in," said McIlroy, who needs the Masters to complete his own Career Slam. "He's shown over the past few years he's mentally very good, so I'm sure he won't have a problem." 

A field with 98 of the world's 100 top players sees reigning major champions Brooks Koepka (US Open), Patrick Reed (Masters) and Francesco Molinari (British Open) grouped together only a wet layout. 

"It's going to be the quintessential target golf," McIlroy said. "Where your ball lands is where it's going to really stay." 

That could reduce some edge for big hitters. 

"Even though it's going to be softer and wet, it's got the potential for I think anybody to work their way up the board," Spieth said. 

Bumpy greens could be a concern, Woods said. 

"I don't think they're going to be the smoothest of greens we've played on, but everyone has got to play them," he said. "We're going to have some putts and they're going to kind of wobble off line." 

"The greens, they look a little worse than they actually putt," McIlroy said. "They look slower than they are."