PEORIA, Ariz. -- He was told he’d need to not knock on the door, but break it down. He was told that the opportunity was there, but that he’d need to wow to earn it. Julio Rodríguez came to Spring Training with a chance of finally achieving a lifelong dream that slowly went from remote to likely to certain.

And now, at long last, J-Rod is officially a big leaguer.

Rodríguez will be included on the Mariners’ Opening Day roster when the club begins the regular season Friday against the Twins in Minnesota. Monday's announcement puts a bow of validation on what was arguably the best camp among the 62 players who initially arrived with Seattle less than three weeks ago.

“It’s time for Julio Rodríguez to play in the big leagues,” Mariners manager Scott Servais said. “He’s just a fun kid, and the joy and the excitement he plays with is contagious. It's going to serve our team very well, and he's a really good player on top of it. It should be fun to see how that plays out.”

The 21-year-old is expected to be the regular center fielder and be a run-producing fixture in a lineup that was the club’s most notable weakness a year ago. He’ll likely hit fifth or sixth in the batting order and see action at all three outfield spots.

• Meet J-Rod, MLB's next superstar

Seattle’s lineup in Monday's 6-3 win over the D-backs could have been a preview of the Opening Day lineup. Second baseman Adam Frazier led off, followed by first baseman Ty France, designated hitter Jesse Winker, right fielder Mitch Haniger, third baseman Eugenio Suárez, Rodríguez, left fielder Jarred Kelenic, catcher Tom Murphy and shortstop J.P. Crawford.

“You work your whole life to get to this point and it’s just amazing, honestly,” Rodríguez said. “To see the expression on [Servais’] face and him telling me, ‘Yo, I think it’s time.’ And I told him, ‘It’s on. I’m ready to go.’”

Over 12 Cactus League games, Rodríguez -- baseball’s No. 3 prospect, per MLB Pipeline -- has shined at the plate, in the field and on the basepaths. In his first at-bat, he crushed a three-run homer that left his bat at 115 mph and traveled 431 feet, and he hasn’t slowed since, going 13-for-31 overall for a .419/.471/.839 slash line and team-leading 1.310 OPS.

His second homer was even more dramatic, an inside-the-parker, in which he encapsulated his opposite-field power, instincts and blossoming speed all in one moment. And after coming up as a right fielder for most of his Minors career, he’s impressed in a transition to center, thanks to thorough offseason training to become a better runner.

“Once I got it going, I put my foot on the gas pedal in this Spring Training and I just kept making my adjustments and going through everything,” Rodríguez said. “That’s when I felt I could make this ballclub, and after these last few days to cap it off, I feel pretty good.”

There have been a few stumbles, notably in a three-strikeout day against the Cubs, when he also had a baserunning blunder and lost a fly ball in the sun. But despite that hiccup, Rodríguez has looked more like a veteran in midseason form than a prospect fighting to win a job. If he’s felt pressure, J-Rod hasn’t shown it.

“There have been a few hiccups along the way -- the game against the Cubs that day, where it didn't go all that great, but that's part of having patience with young players and letting them figure it out,” Servais said.

“There is tremendous upside potential in his ability on the field. The thing that excites everybody is just his joy and passion for playing baseball. He loves baseball. He really does. He loves being a part of what we're doing here and the way it looks. He’s going to be a big part of this going forward.”

Despite his upside, Rodríguez has all of 46 games under his belt above High-A and just 158 Minors games total in the U.S. since signing as an international free agent in 2017. The Mariners are cognizant that struggles can, and likely will, come, but they’re bullish on his mental makeup for when that happens. The young outfielder will also have the support of his teammates and staff to help him navigate the difficulties that come with being a big league player.

“It’s really important when you're dealing with young players that you try to be consistent, so myself, the coaching staff and front office understand the value of that,” Servais said. “Julio is the type that he’s just going to walk in here, and we'll sit down and talk. He likes people. He likes talking. He likes talking the game, and he's OK with a tough conversation, and I've had a few of those in my time with him. He responds very positively.”

Growing up in the Dominican Republic, Rodríguez admired Alex Rodríguez, Ichiro and Manny Ramirez, and he patterned some of his style after them. He still looks up to LeBron James and said he had an epiphany after the 2019 season and tweaked his approach.

“That's when I felt like everything just started clicking and like everything was getting better,” he said. “So, I feel like after the 2019 season, that's when I realized, ‘OK, let's do this right, and let's do the best way we can.’”

Rodríguez has greeted each challenge enthusiastically and passed with flying colors. Now comes the next set of the biggest challenges yet. His body and mind will be tested.

“That's what was in my discussion with him this morning -- that will be the challenge,” Servais said. “Can you keep the joy? I think he can. But he's never done it before, at that level with all the lights on, and then we'll see. The beauty of it is we get the chance to see it play out, give him the opportunity, and let him run with it.”