Top 10 Most Improved MLB Prospects In Full-Season Ball In 2021

Image credit: (Photo by Zach Lucy/Four Seam Images)

The lost 2020 minor league season wasn’t a loss for every player. The 10 prospects highlighted in this piece developed even without traditional player development practices, i.e. games being played to hone skills.

For this exercise, the metric weighted runs above average at was used to compare all players’ offensive production in 2019 versus 2021. That data for minor leaguers stretches back to 2006. Players were filtered for prospect status and to remove those who played in short-season leagues in 2019.

Some examples of players who made dramatic improvements on their 2019 work in short-season ball are Anthony Volpe (+47.8 wRAA), Matt Fraizer (+38.3), Bobby Witt Jr. (+35.3), Riley Greene (+32.2), Everson Pereira (+27.8), Kyle Stowers (+27.5) and Joe Gray Jr. (+26.1). 

The following players took huge strides while moving between full-season leagues. The first two examples were even historic.

1. MJ Melendez, C, Royals
+57.4 wRAA

From one of the worst hitters in the minors in 2019 to one of the best this season, Melendez led the field with 41 home runs and a .337 isolated slugging percentage. Plus, he became the first minor league catcher to reach 40 homers since Todd Greene in 1995. Like Greene, Melendez did his damage at Double-A and Triple-A.

Only one player in the FanGraphs minor league data set, which dates back to 2006, improved by a greater number of runs above average in successive seasons than Melendez. That was Rockies shortstop Rosell Herrera, who improved by 57.7 wRAA between 2012 and 2013. Herrera played in 126 games in 2013, compared with 123 for Melendez this season.

2. Nick Pratto, 1B, Royals
+53.2 wRAA

Pratto was right there with High-A Wilmington teammate MJ Melendez in 2019: near the bottom of the Carolina League leaderboard for OPS. But like Melendez, Pratto adhered to the Royals’ revamped hitting program that began to take shape late in 2019 and used the lost 2020 season to implement changes and overhaul his swing at the alternate training site.

The stakes were higher for Pratto than they were for Melendez because the former was the 14th overall pick in 2017, and because first basemen need to hit to stay in the lineup. Pratto certainly did hit in 2021. He hit in spring training. He hit in Double-A. He hit in Triple-A. He might have hit in Kansas City if teams were not limited to 28 roster spots during September roster expansion. But he never got the call. That must wait for 2022.

Pratto finished second in the minors with 36 homers, third with 98 RBIs and fifth with 83 walks. His wRAA improvement in successive seasons is the third highest turnaround of the FanGraphs era, trailing only Rosell Herrera and Melendez.


3. Jose Miranda, 3B/2B, Twins
+44.2 wRAA

The Twins challenged Miranda to tighten up his strike-zone judgment to impact the ball and tighten up his conditioning to expand his defensive flexibility. He achieved both goals with a breakthrough 2021 season in which he hit .344/.401/.572 at Double-A and Triple-A and led the minors with 184 hits and 306 total bases.   

Drafted as a shortstop out of Puerto Rico in 2016, Miranda started at least 25 games at third base, second base and first base. He even made a few starts in left field and could be the position-flexible righthanded hitter the Twins have been looking for when he debuts in 2022.

4. Brendon Davis, 3B/SS, Angels
+44.7 wRAA

Davis’ adventures in professional baseball began when the Dodgers drafted him in the fifth round out of high school in 2015. Los Angeles dealt him and two other prospects to the Rangers for Yu Darvish in 2017. Davis failed to make much of an impact in two seasons in the Texas system, so the Angels acquired him last December in the minor league phase of the Rule 5 draft. 

Davis began to emerge this season at pitcher-friendly High-A Tri-City and kept up the pace at Double-A Rocket City and Triple-A Salt Lake. He ranked fifth in the minors with 65 extra-base hits as one of 15 players to reach 30 home runs. The 23-year-old batted .290/.361/.561 in 124 games and proved capable on the left side of the infield. 

5. Elehuris Montero, 3B/1B, Rockies
+34.0 wRAA

Montero hadn’t looked his best since 2018, but he made good in 2021 after joining the Rockies organization as the headlining prospect acquired from the Cardinals for Nolan Arenado. Montero dealt with a wrist injury at Double-A in 2019 and struggled through the season. He didn’t ease all concerns with his play in the Arizona Fall League that year or at the alternate training site in 2020.

Montero, who turned 23 in August, gained some measure of redemption in 2021, when he got back on the prospect map at Double-A and Triple-A. He belted 28 home runs and hit .278/.360/.529 in 120 games.

6. Luis Garcia, SS, Phillies
+34.2 wRAA

As odd as it sounds, most players who hit as poorly as Garcia did in 2019 and yet play enough to accrue 27 runs below average are regarded as quality prospects. Garcia hit .186/.261/.255 in 127 games for Low-A Lakewood in 2019, yet played virtually every day because of his quality glove at shortstop and the Phillies’ desire to develop his bat.

Garcia won a Gulf Coast League batting title in his 2018 pro debut, but he owes his 2021 turnaround less to excellence and more to adequacy. As a 20-year-old at the Class A levels this season he was worth 7.1 wRAA, a huge upgrade on his dreadful 2019. Garcia finished the season strong, batting .261/.367/.472 with eight of his 13 homers in his final 45 games.

7. Nick Plummer, OF, Cardinals
+32.0 wRAA

Drafted 23rd overall out of high school in 2015, Plummer didn’t hit much during his first six pro seasons, topping out at High-A. He missed 2016 with a hand injury and 2020 to the pandemic, just like every other minor leaguer.

Things clicked into place for Plummer in 2021 after he had workshopped his swing and let his outstanding batting eye and athletic ability take over. He batted .280/.415/.479 with 15 home runs and 73 walks in 117 games at Double-A and Triple-A. 


8. Jack Suwinski, OF, Pirates
+30.8 wRAA

Drafted out of high school in 2016, Suwinski spent six years in the Padres’ system before joining the Pirates this summer in the deal that sent Adam Frazier to San Diego. The corner outfielder had shown glimpses of ability with San Diego up through High-A, but he didn’t fully blossom until this year, when he began to show power at Double-A San Antonio. 

Suwinski didn’t hit quite as well at Double-A Altoona after the trade, but neither of the 23-year-old’s home parks played well for power. Despite this, he hit a career-high 19 home runs as part of a .262/.383/.485 season in 111 games.

9. Rudy Martin, OF, Royals
+29.9 wRAA

Emmanuel Rivera, 3B, Royals
+28.7 wRAA

The turnarounds by MJ Melendez and Nick Pratto were historic, but those two weren’t the only Royals hitters who roared back to life in 2021. The Royals organization fully embraced technology and different voices from different coaches to teach the system’s minor league hitters. The message got through to many.

Rivera, a 25-year-old corner infielder who had been drafted in 2015, was a leading example. He made his MLB debut at the end of June after hitting .285/.347/.574 with 19 home runs in 67 games, mostly at Triple-A Omaha.

Martin is a lefthanded-hitting outfielder drafted in 2014 who stole 26 bases in 2019 but posted just a .260 on-base percentage in 100 games. This season Martin produced a .389 OBP while stealing 21 bases and drawing 52 walks in 89 games at Double-A and Triple-A.

10. Jonathan Aranda, 1B/2B, Rays
+26.9 wRAA

Aranda went from entering the season as a questionable call for the 40-man roster this November to a no-doubter. His .950 OPS in Double-A South is the eighth highest among qualifiers in the Southern League dating back to 2006. The SL is annually one of the most run-suppressing environments in baseball.

Aranda hit .330/.418/.543 with 14 homers in 100 games this season, most of them at Double-A Montgomery. Scouts are bought in on his barrel accuracy, discipline and impact potential.

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