Magneuris Sierra

Sierra is one of the fastest players in baseball, with 98th percentile sprint speed according to Statcast. The problem is, only the Atlantic League allows batters to steal first base. Until the majors adopts that same rule, it will be tough for Sierra to have fantasy value. He has no power and a bad hit tool, but he can run and can cover ground in the outfield. He is only 24, so there is still room for growth, but it's tough to envision any upside here because the frame is not there to add power, so pitchers will continue to challenge him in the zone and overpower his bat. Expect Sierra to continue on the low-walk/high-contact path he has established throughout his minor-league career.

Acquired by the Marlins last winter, the defensive-minded Sierra opened the 2018 campaign with Triple-A New Orleans, looking to improve his on-base skills so he can take advantage of his 70-grade speed. Unfortunately, things did not go well as Sierra's plate skills fell back from his Double-A marks, registering a 2.8 BB% along with a 25.0 K% in 367 PA with the Baby Cakes. Despite a scant .628 OPS at the time, Sierra was summoned to South Beach after the All-Star break and took over in center field. Sierra held the job for most of the second half even though he slashed an anemic .190/.222/.211 in 156 PA, with only three steals in five attempts. The Marlins are still in rebuild mode while Sierra has options left, so if he fails to impress in the spring, he could be looking at another stint at Triple-A until he demonstrates the ability to get on base at an acceptable clip.

Sierra already has 64 MLB plate appearances despite the fact that he still hasn't mastered Double-A as a hitter. That usage is a bit unfortunate from a developmental perspective, as Sierra was getting rushed by the Cardinals, playing just 20 games at High-A and struggling to make an impact with his bat at Double-A in between brief MLB callups. Thankfully, that usage will be put to an end after he was dealt to the Marlins as part of the package that sent Marcell Ozuna to St. Louis. The elite defensive center fielder will likely be sent back to Double-A, where he can refine his offensive game, as the Marlins won't be contending anytime soon. He remains a 70-grade runner and excellent contact hitter, so he could end up being a poor man's Billy Hamilton in a few years. While the trade may delay his permanent ascent to the big leagues, it will likely work out better for his development in the long run. He could take over as the Marlins' everyday center fielder at some point in the coming years, and could even develop a little power with his new organization.

Sierra has been an enticing prospect ever since he made his stateside debut in 2013, but last year was the first time he lived up to that promise in a full-season league. He showed that he wasn't ready for Low-A in 2015, but he spent all of 2016 with Peoria and the results were outstanding. Sierra stole 31 bases while notching 36 extra-base hits. He is one of those players whose movements on the field stand out, even to the untrained eye. Sierra combines plus-plus speed with an all-fields approach. As he continues to mature physically, more of his doubles will start going for home runs. The primary concern regarding his chances of being a leadoff hitter at the highest level is his low walk rate, but he is such a good baserunner that he still led the Midwest League with 78 runs. This is a prospect worth targeting in dynasty leagues before the entire package starts to come together as he moves closer to the big leagues.

Sierra’s backers were forced to pump the brakes when he failed an optimistic assignment to Low-A Peoria at the outset of the 2015 season. The athletic outfielder hit .191/.219/.247 with a 27.4% K-rate in 190 plate appearances before he was mercifully re-assigned to rookie level Johnson City. However, the 19-year-old then quickly reminded everyone why he was the Cardinals’ Minor League Player of the Year in 2014. He turned in a .765 OPS with three home runs and 15 steals while cutting his K-rate to 17.6% in 239 plate appearances with Johnson City. Despite failing his first assignment to a full-season league, he proved in the second half that the tools of an across-the-board fantasy contributor are still present. Plus speed and an above-average hit tool highlight the package, but many believe more game power will show as he matures. This year it will be important for Sierra to show that he is ready to handle Low-A pitching in his age-20 season.