It's more than just a guy making his Major League debut. Not since Carlos Gonzalez made his debut in 2009 -- he struggled initially, then became the impact player the club projected -- has a prospect entered with such high expectations. Like Gonzalez and shortstop Troy Tulowitzki when he began his first full season in 2007, Arenado is joining a squad that is spawning playoff dreams.
Last season at Double-A Tulsa, Arenado expected a callup. But the Rockies determined in no uncertain terms, and said so publicly, that Arenado did not have the maturity to receive the promotion. Sunday's action shows the Rockies believe differently now.
Now it's up to Arenado, 22, to handle the expectations.
"I just try to do my job. That's the way I see it," said Arenado, who was having dinner with his parents in Tucson -- where Colorado Springs played Saturday night -- when he was informed that he had been promoted. "Hit the ball hard, make my plays and try to help this team win. This team is playing well right now. I want to be a part of it."
A driver was arranged to take him from Tucson to Phoenix, but the driver admitted being tired. Arenado's parents, who were in a different car following the driver, relieved the driver of his duties and completed the trip.
Arenado is following the blueprint set by Tulowitzki and Gonzalez.
Tulowitzki, who has mentored Arenado since the Rockies selected him in the second round of the 2009 First-Year Player Draft, debuted with the lower-division Rockies in 2006. But in 2007, he was able to mesh with his veteran teammates during Spring Training and was inserted as the starting shortstop. Tulowitkzi hit .244 in April, but brought energy and defense, and by season's end was a key cog on a club that went to the World Series.
The last two offseasons, Tulowitkzi has hosted Arenado in Las Vegas for workouts. Tulowitzki has also seen Arenado's growth from his first Spring Training in 2012 to this past spring, when Arenado almost made the team.
"For him, it's going to make the transition a lot easier to have gotten to know the guys," Tulowitzki said. "What you do is worry about the team concept, go out every single day and do what you can to help the team win, and not try to do too much. It's cliché, but I can tell you now it's not easy at all."
Gonzalez debuted with the Athletics in 2008 and was sent to the Rockies as part of the package for star outfielder Matt Holliday before the 2009 season. Like Arenado this year, Gonzalez began '09 in Colorado Springs. In his first 27 games, Gonzalez hit .202 and then-manager Jim Tracy handled repeated questions about sending him to the Minors. Tracy resisted. Gonzalez then hit .320 in the second half to establish himself as a star, and he was their best postseason performer.
Gonzalez sees the same talent in Arenado.
"What it takes is confidence and the opportunity that the manager is going to give you," Gonzalez said. "When you talk about Nolan, you're talking about a guy who's going to play a lot of years in the big leagues if he stays healthy. We don't know anything, but we've got to believe he's going to be an All-Star and be a big part of this team. But right now he doesn't have to think about that. He just has to play, and he'll get to that point."
Manager Walt Weiss placed Arenado seventh in Sunday's lineup, but with Michael Cuddyer and Gonzalez sitting, it was not a normal lineup. Arenado could slip in Nelson's old spot -- eighth -- or Weiss could juggle the lineup to take advantage of Arenado's run-producing potential, yet not hand him too much responsibility.
"The plan is, he's going to be playing a lot," Weiss said. "We'll figure out where to slot him in the lineup. I'm not sure about that yet. It's a tough lineup to crack into the middle, but we'll try to ease him in.
"It's my job to protect him at certain times. Nolan, we all knew, was going to have a big league career. It was just a matter of when. It's today."
When Arenado didn't make the team out of Spring Training, there was public speculation that the Rockies were holding him back to slow his arbitration clock. But with him in the Majors less than a month into the season, if all goes well he could be eligible for arbitration after the 2015 season. This indicates that contract status was not a factor in the Rockies' decision-making process.
"We're just trying to win games," said Bill Geivett, the Rockies' senior vice president of Major League operations. "I know a lot of people were saying there was a financial consideration. We're just trying to put the best team we can on the field."