MLB Rookie Profile: Magneuris Sierra, OF, St. Louis Cardinals

On Sunday the St. Louis Cardinals made an unusual move, promoting outfield prospect Magneuris Sierra to the major league roster, directly from High-A Palm Beach. He is certainly one of the top prospects in the Cardinals system but the decision to skip him past Double-A and Triple-A was certainly unanticipated. Let’s take a look.

The Cardinals signed Sierra in 2012 out of the Dominican Republic, giving him a bonus of $105,000. He emerge as a prospect to watch by hitting .385 in rookie ball in 2014, but was overmatched when he opened 2015 in Low-A, hitting just .191 in 51 games. Sent back to the Appalachian League in June he responded with a .315/.371/.394 mark, then returned to Low-A in ‘16 and hit .307/.335/.395 with 31 steals.

Sierra ranked eighth on the Cardinals Top 20 Prospects for 2017 list with the following commentary:

8) Magneuris Sierra, OF, Grade B: Age 20, signed out of the Dominican in 2012, hit .307/.335/.395 with 31 steals, 22 walks, 97 strikeouts in 524 at-bats in Low-A; lefty hitter with aggressive, slashy approach; power to the gaps at present, may show more home runs in time; would like to see more walks to make his OBP less dependent on his batting average; plus running speed and arm fit well in center but he needs to cut down on errors, which should happen naturally as he gains experience; ETA 2020.

Sierra was excellent in spring training this year, hitting .387/.424/.484. He was off to a decent start at Palm Beach with a .272/.337/.407 line through 81 at-bats, but the promotion to the majors was still a surprise.

Listed at 5-11, 175, Sierra is a left-handed hitter and thrower born April 7th, 1996. There are plenty of tools here, including a 60-arm and 60-running speed. He’s still working out the finer points of baserunning, having been caught five times this year against just three steals, but he has the physical ability to steal 20+ bases per season.

His arm is strong and accurate. He has the tools to be an excellent center fielder although he’s still prone to some route-running mistakes of youth. That’s already shown signs of improvement this year. At this point he is an above-average defender and with more experience he should become elite with the glove.

Sierra is a line drive hitter with some pop to the gaps, although opinions differ on how much home run power he’ll eventually develop. Although not particularly prone to strikeouts, his approach is aggressive and his walk rate rather low.

To be honest, I think Sierra needs more time in the minors. His glove is certainly more than playable now but he needs more at-bats to refine the strike zone and get physically stronger. It will be interesting to see how the Cardinals deploy him.

Here’s a look at that throwing arm.