Sluman birdied No. 17 en route to a 7-under 65 and a one-stroke lead over Couples after the first round in the Regions Tradition, the second of five Champions Tour majors.
Sluman, who had eight birdies, and Couples both had their only bogeys on No. 16 at Shoal Creek.
The Legends of Golf winner with Brad Faxon in April, Sluman matched his best opening round score on the Champions Tour.
Sluman knows the game can shift as swiftly as the weather, which cleared up in time for the round after nearly two inches of rain from Wednesday afternoon into the early morning.
"The greens are very fast out there, but they're as good as we've seen all year certainly, or the last five years that I can remember," he said. "They were just perfect speed and I was getting the ball to the hole.
"On days like today, it feels like it's easy and then sometimes you come out the next day and it feels like an alien took over your body. I hope that doesn't happen to me (Friday)."
Couples, the Presidents Cup captain and World Golf Hall of Famer, made a 20-foot eagle putt on the par-5 sixth hole and a 30-footer for birdie on the next hole. His only blemish was a bogey on the par-3 16th when he overshot the green and landed just into the line of spectators.
The 1992 Masters winner has had a whirlwind few weeks, visiting the White House recently as Presidents Cup captain, playing two rounds with Tiger Woods last week at the PGA Tour's Memorial and getting inducted into the World Golf Hall of Fame in May.
Couples said his golf has been "fair" but called the rest of the year "truly fun." He has endured a memorably bad experience at Shoal Creek.
Couples had four consecutive bogeys to blow a one-stroke lead after 12 holes in the 1990 PGA Championship and lost by three strokes to Wayne Grady.
Couples still likes the course and finished fourth at the Tradition last year.
"I didn't play well at all a couple years ago and then last year I had a good last round to move my way up there," he said. "But I never really had a shot at beating Tom (Lehman). I think I shot a 7 under the last round so I was not even really a factor but at least it felt like I could shoot another good round here. I played really well (Thursday)."
Couples got in 14 holes during the rain-shortened pro-am on Wednesday.
"The fairways were the best they've ever been here for the three years, and the greens took a little bit of water (Wednesday) night that you never saw," he said. "If you were in the rough, you could get the ball on the green. Obviously it made the course play a little easier."
Sluman had few complaints, He nearly managed to save par on 16 and then hit a sand wedge to about 3½ feet on No. 17 to take the lead.
"Relatively speaking, it was a dead-straight putt, the kind of putt you're supposed to make if you've got your name on the bag," said Sluman, who came within inches of a closing birdie.
Waldorf had five birdies on the final eight holes after finishing the first 10 at even par. He said he missed several 10-foot birdie chances but recovered with a nice bunker shot to set up birdie on No. 11 and a 50-footer for another one at the next hole.
"It was almost like I felt like I was prepared for the course and everything, but then two inches of rain came or however much rain came (Wednesday) evening," Waldorf said. "It kind of felt like I was feeling the course out again as far as how the ball was rolling, how the greens were running and all that."
Lehman said "brutal putting" prompted him to switch to a cross-handed grip on No. 8 that he'd been practicing with for the last month, and he had three birdies and a bogey after that.
"Frustration and I didn't feel like I had a chance to make it," Lehman said. "You know how it is when you just feel like you just can't make the putt. I had no confidence so I just changed my grip up and felt more comfortable."