MIAMI -- Marlins right-hander Max Meyer is a cool customer. Teammates, coaches and opponents alike describe him as even-keeled and unrattled.

But even Miami’s No. 2 prospect (MLB Pipeline’s No. 21 overall prospect) felt a little jittery making the long walk from the bullpen to the mound for his highly anticipated Major League debut on Saturday afternoon. That’s when he remembered to tune everything out except for himself, catcher Jacob Stallings and the batter.

“I would say when I got that first out I was relieved, and I was able to kind of take a deep breath and settle in,” Meyer said.

Meyer was chased in the sixth inning of a 10-0 loss to the Phillies at loanDepot park, allowing five runs (two scored after he left the game) on one walk and seven hits while striking out five. Despite that line, there was much to build on moving forward.

With around 20 family members and friends in attendance from Minnesota, Meyer delivered a strike on his first pitch in The Show -- a 94.7 mph four-seamer. His first strikeout came on his slider, which was called the top pitch of the 2020 MLB Draft, to end a 10-pitch battle with Rhys Hoskins. Meyer then worked around a Nick Castellanos double to conclude the first inning unscathed.

The 23-year-old Meyer held the Phillies scoreless until the fourth, when he surrendered three straight two-out hits. Former Marlin J.T. Realmuto turned on a middle-middle 95.5 mph fastball for a two-run homer into AutoNation Alley. Hoskins later took Meyer deep to straightaway center to lead off the sixth. Meyer quickly learned that big leaguers hit mistakes more often; cleaning up his location will be crucial moving forward.

“I thought he had really, really electric stuff,” said Realmuto, who struck out on a four-seamer in their first matchup. “He has a really good slider. Obviously the swing-and-miss stuff -- his fastball is good, he mixed the changeup in when he needed. I thought he threw the ball really well, especially for your first start. He didn't seem like he was nervous out there. He seemed like he had good control on the mound, good confidence. He looks like he's going to be a good pitcher for a long time.”

Even after Realmuto and Hoskins’ homers, and even when manager Don Mattingly took him out after Realmuto’s double put two in scoring position with Miami down 3-0 in the sixth, Meyer’s body language didn’t change. Throughout his economical 79-pitch start, he remained on the attack. He competed. He wasn’t afraid.

Meyer’s ability to control his emotions reminds Stallings of former teammate Joe Musgrove. That, combined with his competitiveness, will serve him well moving forward.

“It'll be huge,” Mattingly said. “Almost everybody you see now has good stuff. You see these guys with stuff, and it's a guy that has the understanding of how to get better, and the belief in himself to continue to work, to learn to keep always evolving, and what that means here. Those are the guys that end up being the better guys.”

Ever since he was selected third overall in the 2020 MLB Draft, Meyer has been tabbed as a dude. Pitching coach Mel Stottlemyre Jr. heard about it from other members of the organization, and he saw glimpses of it the past two Spring Trainings.

Saturday offered a reminder that Meyer isn’t a finished product. He will go through the same growing pains as veteran rotation mates Sandy Alcantara and Pablo López. The Majors are not a linear journey.

Alcantara posted a 4.32 ERA in eight relief appearances with St. Louis in 2017 before notching a 3.44 ERA in six starts with Miami in ‘18. He is now a two-time All-Star and one of the Majors’ best pitchers. López compiled a 4.76 ERA through his first 31 starts, then a 3.10 ERA in the 49 starts since.

“[Meyer is] like all young pitchers. He's going to go through it and get to a point where he can figure out where his adjustments are,” Stottlemyre said. “Every guy I've ever had has gone through that process. I love the stuff. I love the competitive nature. This guy wants the ball in big moments. [Triple-A pitching coach] Jeremy Powell has done a wonderful job in helping shape this player and get him to a point where he can get here and compete and help us win.

“We went through it with Sandy and López where we spent a lot of time watching the bumps and the bruises and the hard lessons and having to take it onto the chin often. You don't want to have to do that too often. Those guys had to learn how to pitch up here in the big leagues.”