MIAMI -- When Marlins left-hander Braxton Garrett broke the news of his callup over the phone to his family, the excitement was palpable. But when it came time to take the mound for his Major League debut on Sept. 13, a different feeling sank in. Top prospect Sixto Sánchez had just pitched a seven-inning shutout in the opener of a doubleheader during a pivotal 15-game homestand.

"That made it a little bit more nerve-racking knowing I had to follow that up," Garrett quipped last week.

Turns out Garrett had nothing to worry about. He limited the Phillies to an Alec Bohm solo homer in five frames, with six strikeouts and two walks, in an 8-1 victory at Marlins Park. Garrett even went viral because of his reaction to third baseman Brian Anderson's defensive gem.

Garrett's encore a week later in another doubleheader didn't go as well. He surrendered five runs (four earned) on five hits (including two homers) and three walks in 2 2/3 innings in a loss to the Nationals. But Garrett discovered -- in a two-start sample -- that his stuff plays.

According to MLB Pipeline, Miami's seventh-ranked prospect can locate all of his pitches and knows how to sequence them to set up hitters. Garrett's fastball, which usually ranges from 90-93 mph and tops out at 96 mph, averaged just 89.6 mph per Statcast in his brief callup. It should play up because of his command and its downhill angle. Garrett's changeup, which he threw 14.6 percent of the time, should give him a solid third pitch with more development.

The 23-year-old southpaw's best offering has always been the curveball, which he has thrown with the same grip since he was 12. Of the 42 times Garrett threw it, batters picked up just one hit and whiffed 50 percent of the time. It's a low-80s bender with good depth that works against both lefties and righties.

"The velo was down just a little bit," Garrett said. "I'm not sure really the reason. It was just down, but not something I'd necessarily worry about too much. I don't know if I'll ever be a real velo guy. My curveball is very effective. We've gone back and looked at the numbers on that, so that's a real positive thing to come out of those starts just to know that it plays. That pitch when I'm throwing it for strikes and effectively, it makes all my other pitches much better as well."

This offseason, Garrett has used that experience to prepare for what 2021 has in store. Last week, he participated in the Rookie Program, an annual event that provides top prospects with resources to learn about how their lives will change in the big leagues. In collaboration with the Major League Baseball Players Association and the Commissioner’s Office, the orientation seeks to help prepare the young players -- from dealing with media to handling their finances to health-related topics. The 30th iteration was done virtually because of the COVID-19 pandemic.

Current and former Major Leaguers including Francisco Lindor, Andrew Miller and Curtis Granderson spoke to the group. Garrett, who received his invitation in December, didn't know about the initiative beforehand.

"It's great to hear just coming from them, big leaguers who have done it and have been doing it for years," Garrett said. "It's cool that they show they care and take time out of their day to come on Zoom to talk to us rookies. It's really cool. Even when I was up in the big leagues, just getting to talk to those guys and pick their brains with anything is always great."

It has been quite the journey for Garrett, whom the Marlins selected seventh overall in the 2016 MLB Draft (highest-taken Alabama prepster since 1971). Expected to quickly rise because of his advanced pitching profile, he instead underwent Tommy John surgery just four starts into his professional career. Garrett called it a shock because he never had problems with his arm, shoulder or elbow before.

As a result, a two-year journey began. Garrett missed all of the 2018 season, then started to feel normal midway through '19, when he went 6-6 with a 3.34 ERA in 20 starts at the Class A Advanced level. He would have led the Florida State League in strikeout rate (10.1 per nine innings) if he hadn't fallen just shy of qualifying. Garrett received a one-game promotion to Double-A to close out '19.

Despite having thrown just 114 1/3 innings over the past two years, Garrett isn't too concerned about workload management in 2021. He pitched at the alternate training site in Jupiter, Fla., with the other prospects who were part of the 60-player pool for the '20 season. During the shutdown, Garrett still was able to pitch against live hitters.

"Mostly just working on my fastball command," Garrett said of this offseason. "That was one thing towards the end of the year last year that got away a little bit that I usually have pretty honed in. All pitchers are always working on their command. Secondly, the development of my changeup. I'm much more comfortable with it now than I was two years ago, and it's really coming along. I had two starts, so it's not a ton of work to look back on, but just the normal things. Getting my pitches better, getting stronger. Putting on a little bit of weight will help as well."