The Diamondbacks went on beat Cincinnati 4-3 in 11 innings.
"This was a game to put in a time capsule and let people of the future watch it," Johnson said.
Johnson became the first left-hander to strike out 20, but didn't join Roger Clemens and Kerry Wood, who share the record for strikeouts in a nine-inning game.
Randy Johnson tied a MLB record with 20 strike outs in nine innings.(AP Photo)
The Elias Sports Bureau, baseball's statistician, said Johnson's performance will be considered as occurring in an extra-inning game even though he came out after nine.
The major-league record for an extra-inning game is 21, by Tom Cheney for Washington against Baltimore in a 16-inning game on Sept. 12, 1962.
"I was asked if I wanted to go out there and saw no point in going out there for the 10th inning," Johnson said. "I surely could have went out there and done it, but what was the point in going out there and throwing 10 innings?
"I really didn't see it."
Johnson wasn't disappointed, though.
He wanted to turn the game over to the bullpen.
"The outcome is what's important," he said.
Clemens struck out 20 for Boston against Seattle on April 29, 1986, and did it again for the Red Sox at Detroit on Sept. 18, 1996.
Wood struck out 20 for the Chicago Cubs against Houston on May 6, 1998.
Mark Grace, who hit a game-tying double in the 11th, played in Wood's game.
"There really wasn't much difference," Grace said. "They both had that electric slider going."
Centre-fielder Steve Finley has never seen a slider on a par with Johnson's.
"It was ridiculous," Finley said. "You know, he throws that batting-practice fastball 92 or 93, and there were a lot of times tonight I thought he was throwing his fastball that speed, and it was 98.
"It was so easy, with no effort, on any of his pitches, sliders, everything."
Johnson threw 124 pitches, 92 for strikes, and walked none before Byung-Hyun Kim relieved to start the 10th.
Johnson struck out the side in the fourth, seventh and eighth innings, and fanned two batters in the first, second, third, fifth and ninth.
He struck out only one in the sixth.
The 37-year-old pitcher, known as the Big Unit, won the last two NL Cy Young Awards and the AL Cy Young in 1995.
He had 18 strikeouts in the first eight innings, then struck out pinch-hitter Deion Sanders on three pitches leading off the ninth.
Johnson gave up a groundout to Donnie Sadler, then struck out Juan Castro swinging.
The pitcher raised his right arm in celebration and tipped his cap as he walked off the field.
Bank One Ballpark put a "K" on the scoreboard for each strikeout, but the board ran out of room before Johnson reached 20.
Additional "Ks" were then tacked on the side of the board, with lights forming "20" in the middle.
Johnson struck out Barry Larkin and Alex Ochoa three times apiece; and Castro, Pokey Reese, Chris Reitsma, Ruben Rivera, Sadler, Kelly Stinnett twice each.
He fanned Aaron Boone and Sanders once.
Johnson, who struck out nine of his first 12 batters and eight of his last nine, allowed three hits.
He had a perfect game going until Boone singled with one out in the fifth.
Boone stole second and scored when Rivera singled up the middle. Cincinnati's third hit off Johnson was a sixth-inning single by Sadler.
The Diamondbacks tied it on an RBI single by Reggie Sanders in the sixth off Reitsma.
Cincinnati went ahead 3-1 in the 11th when Russ Springer loaded the bases on two walks and an error, and Ochoa hit a two-run sacrifice fly to deep centre field off Troy Brohawn (1-1).
But Grace hit a two-run double and pinch-hitter Matt Williams walked with the bases loaded in the bottom half off Danny Graves (1-1), who blew a save for the second time in 11 chances.
Graves was philosophical about it, and couldn't help but admire another pitcher's tour de force.
"It just wasn't meant to be tonight after what the Big Unit did," Graves said. "Striking out 20 guys?
"You kind of think there's no way we should win after the performance he had. Congratulations to him, and its too bad he didn't get the win out of it."
Johnson had twice struck out 19 in a game for Seattle, on June 24, 1997, in a 4-1 loss to Oakland and that Aug. 8 in a 5-0 win against the Chicago White Sox.
"I've struck out 19 before and lost and I've struck out 19 and won," he said. "I get a no-decision today, but the team won, and that's the bottom line."
The only other left-hander to reach 19 was Steve Carlton, who did it against the New York Mets for St. Louis on Sept. 15, 1969 -- losing the game 4-3.
With 3,132 strikeouts, Johnson passed Bob Gibson (3,117) to move into 11th place on the career list.
Ferguson Jenkins is 10th at 3,192.
Nolan Ryan holds the record with 5,714.
"The people that I'm in a category with now, I feel extremely honoured to be included in that category," Johnson said.
It was his sixth consecutive game with double-digit strikeouts and seventh in his eight starts.
He has 155 in his career, second only to Nolan Ryan's 215.
Cheney struck out batters in each of his last two innings to reach 21, going the distance.
Johnson is 39-19 since joining the Diamondbacks for the 1999 season.
By Mel Reisner