ST. LOUIS -- When MJ Melendez went into the dugout in the bottom of the sixth inning of Triple-A Omaha’s game against the Mud Hens on Sunday, manager Scott Thorman asked him to take off his sunglasses.

Melendez was confused. He usually wears them during day games, so why would he take them off? Turns out, Thorman wanted to look Melendez in the eyes when he told the 23-year-old he was going to be a big leaguer.

“He sat next to me and said, ‘This is not the way I imagined it, but you’re a big leaguer now,’” Melendez said. “And I just shook his hand and gave him a hug, and a couple tears came.”

• What to expect from MJ Melendez

The Royals called up their No. 2 prospect when backup catcher Cam Gallagher went on the 10-day injured list with a strained left hamstring. Melendez called his family to share the news, then packed his stuff and flew from Omaha to St. Louis on Sunday night, scrambling to join the team in time for Monday’s makeup game against the Cardinals.

“It was a very emotional moment,” Melendez said. “I think from the moment I was told by my manager and talked to my family, I kind of saw a glimpse of everything leading up to this moment and taking everything in and realizing all the stuff, all the hard work that I put in, it’s finally gotten to this moment. Just really grateful for that.”

Now that Melendez is in the big leagues, it’s reasonable to wonder what his role will be. Melendez, who was not in the starting lineup on Monday and did not enter the game, has turned himself into one of the most well-rounded catching prospects in baseball, an impact left-handed bat at the plate and a plus defender behind it.

But with veteran Salvador Perez still catching most games, the Royals will walk a fine line of finding Melendez playing time while ensuring they still have a backup ready to go in case Perez goes down with an injury. When Gallagher was injured on Sunday, the Royals moved Perez from DH to catcher, losing the DH spot in the fifth inning and hoping Perez didn’t get hurt.

First baseman Carlos Santana is the emergency backup catcher, but manager Mike Matheny wants to avoid that scenario at all costs. There also will be pressure to make sure Melendez, who is a big part of the Royals’ future, doesn’t sacrifice his development because of a lack of playing time.

“It’s not all scripted out,” Matheny said. “We just go one day at a time, let [Melendez] know we’re going to use him when he gives us the best chance for us to win. To stay ready with his bat. It’s a little dicey, though, when you don’t have another backup catcher. That’s a position that you can’t just pull somebody off the field and put them behind the plate. It’s a little bit of a challenge, more so than most other positions.”

Perez typically gets one or two days off from catching a week, serving as the DH, so Melendez will slot in the lineup on those days. The Royals also explored playing him in the outfield in Omaha, and he worked closely with longtime coach Rusty Kuntz to improve his jumps and reads.

Club officials were pleased with how Melendez handled playing right field, but it remains to be seen how many opportunities he’ll get there. The Royals are also balancing playing time for outfielders Kyle Isbel and Edward Olivares, both of whom are better defenders and have proven their bats are Major League-ready, too.

“He can play there,” Matheny said of Melendez’s in right field. “Being able to play there and being a top-tier defender are two completely different conversations. … Once again, we’ll figure out where his opportunities present themselves. But we’ve got to be really careful. There will be times where you have that left-handed bat, but once again, you burned your backup catcher, that’s a scary place to go.”

Melendez, for his part, is just ready to play wherever and whenever that time comes.

“I love being able to take on new roles, whatever I can do to help the team and show what I can do,” Melendez said. “Wherever the team needs me, honestly. … I know that I can go out there and feel comfortable and just let my abilities take over.”