Back then, nearly 14 years ago, the young, scowling 6-foot-10 fireballer was tough to hit he just wasn't quite sure where the ball was headed once it left his hand.
Now, at 40, the man nicknamed the Big Unit has aged to perfection.
Johnson became the oldest pitcher in baseball history to throw a perfect game, retiring all 27 hitters he faced in the Arizona Diamondbacks' 2-0 victory over Atlanta on Tuesday night.
"I've still got a great deal of pride," he said. "I feel like I'm throwing as good as I've ever thrown."
With his sizzling fastball and nasty slider, Johnson struck out 13 and went to three balls on just one hitter.
Johnson's was just the 17th perfect game in major league history, the 15th since the modern era began in 1900 and the first since the New York Yankees' David Cone against Montreal on July 18, 1999.
"Everything he's done up to this point pales in comparison," Arizona manager Bob Brenly said.
That's saying a lot. Johnson has won five Cy Young Awards, put up staggering strikeout numbers and helped Arizona win the World Series in 2001.
Now this, the rarest of pitching feats.
Johnson became the 27th pitcher to throw two no-hitters, and the nearly 14-year span between them was longer than anyone else. His first came for Seattle on June 2, 1990, when he no-hit Detroit but walked six.
"That was far from perfect," Johnson recalled. "I was a very young pitcher who didn't have any idea where the ball was going. I was far from being a polished pitcher. Fourteen years later, I've come a long way as far as knowing what I want to do."
Cy Young had been the oldest to throw a perfect game, doing it in 1904 at age 37.
Johnson struck out the final batter, pinch-hitter Eddie Perez, with a 98 mph fastball.
He pumped his fist and raised his glove, a rare grin spreading across his rugged face. He started to put out his hand when Robby Hammock arrived at the mound, but the young catcher a foot shorter than Johnson gave the pitcher a bear hug instead.
Within seconds, Johnson was mobbed by beaming teammates.
"I'm happy that they showed a little more emotion than I did," he said. "After a nine-inning ballgame, I'm pretty tired. I will probably take it in, maybe (Wednesday). But right now, I'm pretty tired."
Johnson threw 117 pitches 87 for strikes. He dominated with two pitches, mixing a fastball that got faster as the night went on with a devastating slider.
"My slider was probably as a sharp as it's been," he said.
The Atlanta fans began cheering Johnson in the eighth inning, and the feat stole the spotlight at ballparks around the country as the final outs were shown on big screens.
Johnson (4-4) is only the fifth pitcher to throw no-hitters in both the National and American leagues, joining Young, Jim Bunning, Hideo Nomo and Nolan Ryan.