American Woods, who clinched last year's title at Southern Hills, has been sidelined since his U.S. Open victory in mid-June after having reconstructive knee surgery.
"I feel it's exciting times," South African Els, 38, told reporters on Wednesday before playing nine holes of practice on the undulating South Course at Oakland Hills Country Club.
"It's an opportunity for a lot of guys. You look at guys who have not won majors, who are my age or even past my age who are playing well this year, they can break through.
"If you look at the world rankings from fifth to 20th, there's a lot of guys very bunched and playing very good golf. There are so many guys that can win (this week)."
Els, a former world number one who has claimed two U.S. Opens plus the 2002 British Open, is frustrated he has not earned more major titles in his glittering career.
"I've had my fair bit of chances," the 16-times PGA Tour champion said. "I've had quite a few second places, quite a few thirds and top-fives, so quite a few chances.
'Way Better'
"But I think Tiger a lot of times has just been way better," added the world number five. "I remember in 2000 finishing second three times, and twice to him in majors."
The South African was runner-up to Woods in the 2000 U.S. Open at Pebble Beach and also at the British Open one month later at St. Andrews.
"You can only do what you can," said Els, who has piled up six runner-up spots in the majors. "I feel I've still got quite a few years left so I've got to keep pushing away.
"I get criticized in South Africa a lot more than I get over here. It's something that I've had to live with for a while. If Tiger Woods wasn't around, I probably would have won a couple more (majors). But I don't feel like I'm done yet."
Els, popularly known as the 'Big Easy', likes the look of the par-70 South Course at Oakland Hills where he tied for fifth at the 1996 U.S. Open.
"I've got a very good feel about the golf course," he said. "My swing is in pretty good shape and I feel excited about this week. I feel like I have a reasonably good chance at making a good showing and hopefully I have a chance on Sunday."
Els is scheduled to tee off at 1355 local (1755 GMT) in Thursday's opening round in the company of Australian Adam Scott and American veteran Fred Couples.
