He's a sure-fire baseball Hall of Famer, excelling as both a starting and a closing pitcher.
He won a World Series and pitched in a few others, including perhaps the greatest Game 7 duel of all time against Jack Morris.
In his spare time he's also a pretty fair golfer, carrying a plus-2 handicap and once shooting rounds of 69 and 67 in the same day while playing with his buddy Tiger Woods.
Given all those athletic talents, Smoltz put his hobby on display at last week's Nationwide Tour event in Valdosta, Ga.
"I just want to see what it's like," he said. "I want to know what my body feels like. I want to know if that tension creeps up."
Well, it probably felt a lot like giving up 10 runs in the top of the first to the Pirates. Smoltz shot 84-87 in the South Georgia Classic at Kinderlou Forest to miss the cut by 27 shots. He was nine strokes worse than the next-to-last golfer. Given a stroke for each of his 36 holes he'd have only been tied with the halfway leader, Jon Mills.
"Never in a million years did I think I could shoot two rounds like that, but it happened," a humbled Smoltz wrote in his online diary.
That right there displays the naivete of a gifted athlete. Smoltz was doomed to fail before he ever teed it up with the pros on a 7,700-yard course that ranks as one of the toughest on tour. He was as doomed as NFL Hall of Famer Jerry Rice has been in three failed attempts on the Nationwide Tour himself.
Great golf can certainly be played by men in their 40s, but those men were most likely playing great golf in their teens, 20s and 30s. They didn't just show up with their recreational game and expect to compete with guys who've been pursuing this game all their life.
"Smoltz is a phenomenal athlete and a very solid golfer and I honestly think he has a chance to play golf at a very high level," said tour veteran Dicky Pride, who is teeing it up in this week's Nationwide Tour event in Athens, Ga. "But you can't put 20 years into something else and expect that 20 years to be made it up in a matter of a few years, especially in golf where he's trying to beat people at their first sport with his second sport."
Nationwide Tour veteran Trevor Murphy gets where Smoltz is coming from. Murphy was an Olympic-caliber skier as a kid before a knee injury pushed him toward a different competitive career. So he gets that feeling of ego and invincibility that stellar athletes have.
"Being as competitive as I am I kind of felt like the process didn't apply to me," Murphy said. "Where's the shortcut for me? I felt like I didn't have to go through all this stuff."
In golf, however, the process is everything. It takes hours and hours, day after day, year after year to get good enough to even sniff the kind of game that mini-tour golfers have. Smoltz was bypassing the whole process with a game he honed with his pals on off days with the Braves.
"To play golf at this level though certainly makes you realize what these guys do for a living, how much they grind at it, how much they practice," Smoltz admitted. "They know every one of their shots."
What's Smoltz missing that hundreds of pro golfers you've never heard of have?
"About 25 years of doing it since you were a kid," said Jason Gore, a former PGA Tour winner trying to work his way back into the top tier.
"Smoltz and Rice, they are world-class athletes," Gore said. "And I think they expect to be able to come out here because they can shoot 66 on their course. 'I was the best at what I did, why can't I do that?' But they've been training other muscles and doing their thing."
Their thing -- in both baseball and football -- fed off the energy of the games. They were in the moment. Golf, however, is about control and harnessing emotions. And if you're having a bad day, there's no Bobby Cox to take you out or Bill Walsh to regroup things at halftime.
With 17 bogeys, four doubles and a triple in Valdosta, it was a nightmarish experience Smoltz likened to his first outing as a closing pitcher for the Braves when he gave up eight runs.
"Humiliating baseball experiences made me a better person and a better ball player," he said on the Golf Channel's Morning Drive on Tuesday. "I will be a better golfer having gone through what I did and dealing with what I dealt with versus coming out there and surprising the world."
With six years to go before he's eligible to pursue a career on the senior circuit, Smoltz needs to do more than beat balls on the range and make a few cameo appearances on a sponsor exemption on the Nationwide. If he's serious about making a go of it in golf, there are mini-tour events and Monday qualifiers that will teach him how to survive in competitive golf.
"He's never going to get anywhere without a commitment," Pride said. "Just because he's a phenomenal athlete and he knows how to play baseball better than anyone out here doesn't mean he can just show up and play better than guys. If he wants to play golf he needs to commit himself to playing golf and doing what it takes to get better. That's the way it is for everybody. With his competitive instincts he's got a chance. If John wants to do TV and be a part-time golfer, I don't think he'll be successful."
That's a tough reality for someone like Smoltz to take. But golf at this level is not for hobbyists. Even a Hall of Famer has to earn it in the dirt.