"He walked into my office," Gibson said. "And I asked him, 'Miggy, do you want to go to the All-Star Game?'
"He was stunned a little bit," Gibson continued. "He said he thought he was going to cry for a second."
And despite All-Star break travel plans, Montero did indeed want to go to the All-Star Game.
So he stepped out of Gibson's office in St. Louis on Sunday, called his wife, his mom and, on Tuesday, will join right fielder Justin Upton as the pair of D-backs competing in front of their hometown fans in the 82nd All-Star Game at Chase Field.
"It was emotional," Montero said. "There were a lot of things going through my head. I'm an emotional guy and it was a great feeling, but it's hard to describe."
"I've always thought about playing in the All-Star Game," he said. "It means a lot. I've always wanted to be here, and I hope it's not the first and only time."
Montero was chosen by National League Manager Bruce Bochy to replace Phillies third baseman Placido Polanco. Montero is hitting .272 with 10 home runs and 45 RBIs in 81 games.
"He's having a good year," Bochy said Monday during the All-Star Game press conference, noting that he also chose Montero to give the NL squad a second catcher and a left-handed bat for flexibility late in the game.
"It's awesome," Upton said about Montero making the team. "I wasn't surprised, though. He's had a great year. I know he's excited, and I'm excited to have him right here alongside me."
Gibson, who, along with Montero, is attending his first All-Star Game, said that the honor is a testament to how far the 28-year-old catcher has come.
"And how much he means to our team," he said. "I think if you sit down and look at the numbers, next to [Braves catcher Brian] McCann, he's up there.
"He's on pace to play more games than he's ever had, he's healthy, has a lot of energy and I hope he can carry it through the rest of the season."
The first-time appearances by Montero and Gibson make the 23-year-old Upton, in his second All-Star Game, the grizzled veteran of the group.
"I didn't know what to expect last time," he said about his first All-Star appearance, in 2009 at St. Louis.
"This time, I've done it before. It makes it a little easier, but you still don't know what to expect."
The right fielder has 15 home runs, 46 RBIs and is hitting .293 at the break. He is largely regarded as one of the brightest young stars in baseball, and feels proud to represent the D-backs in the city of Phoenix.
"It's going to be pretty busy, but it will be fun," Upton said. "This is our first time hosting it, so I'm going to enjoy it."
"We're getting there," he said of the D-backs' fan base building a baseball tradition. "If you bring in this type of atmosphere to Chase Field, I think the fans will realize what we're all about and hopefully they can jump on."
The addition of Montero to the NL roster gives the D-backs two representatives, and a huge addition it was for a fan base that looked to be short of multiple representatives when starting pitcher Ian Kennedy didn't win the All-Star Game Final Vote.
"We needed more than one guy," Upton said. "I just felt like, with the All-Star Game in your hometown, you should have more than one guy."
The trio of Upton, Montero and Gibson gives them three, and after passing on All-Star Games in the past, the D-backs skipper seems more than ready to embrace the environment on Tuesday.
"I'm just going to take it all in," he said. "All these guys here are top-notch athletes, and it's going to be good to get to know them as people.
"I know I'll enjoy it."
Anthony Fenech is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.