"I just feel like there's not a lot more for me to do in this game," Johnson said. "Eventually you have to say it's time."
Johnson, 46, was with the D-backs for eight seasons from 1999-2004 and again from 2007-08.
"The time I spent in Arizona was pivotal because that was the greatest run I ever had," Johnson said this past spring. "It's comparable to anybody at any period in the game, and it's where I won my only championship."
There were many highlights during Johnson's career, but certainly some of the top ones came during his first stint in Arizona.
After the D-backs finished 65-97 in their inaugural season of 1998, then-owner Jerry Colangelo decided to be aggressive in the free-agent market. His first big target was the 6-foot-10 Johnson, who signed a four-year $53.4 million deal.
"It was a huge deal," then-general manager Joe Garagiola Jr. said of that news conference in December 1998. "I remember literally thinking, 'We got him. We signed Randy Johnson.' It was a tremendous coup."
It turned out to be the best signing in club history as Johnson won four consecutive National League Cy Young Awards and compiled 81-27 record to go with a 2.48 ERA over that span.
Curt Schilling, Johnson's teammate from 2000-03, saw Johnson at his best. The pair formed a one-two punch at the top of the rotation that drew comparisons to the Dodgers' Sandy Koufax and Don Drysdale.
"For two years, I have never witnessed the complete domination, day in and day out, he brought to the game," Schilling said. "There were nights he made the best players, best lineups and best teams look like he was in a league above them. His intensity and 'anger' were unparalleled. I could never get to that 'place' he could when I pitched -- I enjoyed it while I was doing it, I think. He was a miserable and angry man on the days he had the ball. He's the most dominating pitcher I ever played with at any level."
The highlight of Johnson's career from a team perspective came in 2001, when he went 21-6 with a 2.49 ERA and led the D-backs to a World Series championship.
"This is a team game, 25 guys and a coaching staff and the main objective that you play for when you go to Spring Training is to get to a World Series," Johnson said. "I would have to say the pinnacle of my career was to be able to do my part to get the team to the World Series and do my part in the playoffs and do my part in the World Series. That's probably my crowning achievement from a team standpoint."
THE CY YOUNG YEARS
Johnson did his part and then some that year. Not only did he win Games 2 and 6 of the World Series, he also picked up the win in relief in Game 7.
"He was one of the greatest pitchers of all time and one of the most intimidating players of his era," D-backs GM Josh Byrnes said. "He certainly will be an unforgettable part of Diamondbacks history."
While Johnson had plenty of individual highlights, two that certainly are near the top of the list are the 20-strikeout game against the Reds on May 8, 2001, and the perfect game he threw against the Braves on May 18, 2004, in Atlanta.
"To throw a 98 mph fastball in the ninth inning for the last out of the game, I still remember that," Johnson said. "It says a lot about what I was about when I was out there."
Johnson was asked Tuesday which hat he would like to wear when he enters the Hall of Fame five years from now. Of the teams he played for, Johnson spent the most time with the Mariners (nine-plus years) and the D-backs (eight).
A less than amicable parting from the D-backs after the 2008 season left a bad taste in Johnson's mouth. While players get some input into the decision, the Hall of Fame makes the final decision and it would seem like the D-backs would be the logical choice given his accomplishments there.
"That's a good question," Johnson said of his cap choice. "I played for a lot of teams and a lot of teams I feel I made my mark with, but that's really a decision that's out of my control. I believe it's something that's decided for you. I'm not even 24 hours into my retirement yet so I will wait down the road and consult with whoever I have to consult with if I'm elected to the Hall of Fame."
After his likely induction into the Hall of Fame, the D-backs plan to retire his number. Club policy is that only players in the Hall can have their numbers retired.
One of the contracts Johnson signed with the D-backs included a personal-services contract.
"I have a one-year service agreement with them, so at a later time I'll get together with them and we'll discuss that," Johnson said. "Right now I just want to kind of enjoy this retirement, see what retirement is all about."
D-backs president and CEO Derrick Hall said he will need to review the personal-services agreement, but he believes the team has a year to employ Johnson for a minimum of five years.
"I certainly want to sit down with Randy at some point soon to discuss things," Hall said. "Randy had some of his best years while with the D-backs, providing Hall of Fame memories for our great fans. He is an important part of our celebrated history, and we salute him on a remarkable career and thank him for his contributions to our franchise."
For now, Johnson wants to enjoy playing golf and taking his kids to school. At some point, though, he said he would like to get back in the game.
"I'm sure in due time I will be itching to do something baseball-wise," Johnson said. "I wouldn't say I'm going to cut the ties because the one thing that I've really enjoyed doing the last few years -- for anyone that wants to listen -- is help people. I really had a lot enjoyment being in San Francisco this year and talking with Matt Cain or Jonathan Sanchez. I think I would like to coach down the road."
Steve Gilbert is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.