MIAMI -- Like any prospect, Marlins left-hander Braxton Garrett is a work in progress. In Wednesday night’s 4-3 loss to the Rockies at loanDepot park, he proved that in his first Major League start of 2021. With three starting-pitching options landing on the injured list since last Thursday, Garrett returned to the Majors out of necessity.

Miami’s No. 7 prospect trailed six pitches in, when Charlie Blackmon drove in Raimel Tapia with a single. He would escape further damage on a lineout with a pair of runners on base. In the third, Blackmon reached on a dribbler down the first-base line, moved to second on a groundout and scored on Yonathan Daza’s single.

• Box score

Garrett must locate his fastball to both sides of the plate to be successful. He had trouble doing so on Wednesday because he was nitpicking, falling behind to eight of 18 batters and reaching 10 two-ball counts. At least two batters reached in all four frames. The four-seamer recorded seven called strikes, two whiffs, three fouls and six balls in play -- two for hits. Still, he bent but didn’t break across four innings of two-run ball.

“It didn't look like he had his best stuff,” manager Don Mattingly said. “I think more than anything, it didn't seem like until that last inning he really located his fastball where he could use that thing to keep them off-balance. I felt [catcher Sandy León] did a nice job of mixing breaking balls, being able to stay soft, kind of navigating the traffic. Obviously Brax had to execute that part of it.”

There were some interesting trends in Garrett’s return to the big league mound:

The slider

Although his curveball (60) has the highest grade on the scouting scale, Garrett threw it just seven times out of his 77 pitches -- what he believed to be the fewest he has thrown “in a long time.” He instead relied heavily on a four-seam (50 grade)/slider combination out of his four-pitch mix. The slider resulted in just one hit and three outs.

“I threw the slider a lot tonight, just with the game plan, seeing with a lot of guys my slider played better,” Garrett said of his newest pitch. “I'm comfortable with it. It's getting better. If I can keep it short and not real big, that's where it plays best. I got away from the curveball a little bit. I probably could've thrown it a little bit more.”

Down in velocity

Garrett averaged just 89.8 mph on his 37 four-seamers, maxing out at 91.2 mph. During his two starts in 2020, the southpaw averaged 89.6 mph on the pitch. According to MLB Pipeline’s scouting report, he was sitting at 90-93 mph and topping out at 96 mph in 2019.

“There's certainly more in the tank,” Garrett said. “I think I was talking with [pitching coach Mel Sottlemyre Jr.] about that after my start. There's just some things my lower half and upper half are kind of out of sync a little bit, because my hips kind of go and my upper half kind of stays back, and they're really just not in sync. So I certainly think there's more in the tank there. But it's just a matter of getting my body to work.”

Until his next time on the mound, the 23-year-old Garrett will continue working. Without a Minor League season in 2020, '21 is even more important for a prospect’s development path. After he appeared out of Miami’s bullpen on May 15, Garrett went back down to Triple-A Jacksonville and posted a 1.69 ERA and held opponents to a .237 average and .591 OPS in three starts.

"When he had come up before -- he's got that really good secondary stuff -- but to be able to get in good counts and to be able to get his fastball in the zone in good spots, that's going to be important,” Stottlemyre said over the weekend. “So we needed to go finish him off a little bit in the Minor Leagues and let him get those innings and work through that stuff.

“He has shown that, and he certainly is one of our prospects throwing the ball well and has to be in that discussion where we're talking about him now. Let's see where that lands, but he's one of the guys that certainly has some promise and now has four pitches and is doing some good things in the zone that we like what he's doing."