Chicago Cubs Prospect Update: When Will We See Jonathan Sierra’s Power?

Jonathan Sierra is still only 20 years old and he’s playing almost every day for South Bend. At 6-foot-3 and 225 pounds, he’s the kind of physical specimen who passes the eye test with flying colors. The At some point, he should break out. At some point…

Basic Info
6’3” and 225 lbs.
Bats/Throws: L/L
Signed as a Free Agent from Dominican Republic in 2015
ETA: 2023

When the Cubs signed Sierra four years ago in international free agency, the thought was that his ability was similar to Eloy Jimenez. Jesse Sanchez of even compared Sierra — who went by Yonathan Sierra Estiwal before he was signed by the Cubs — to Darryl Strawberry in 2015:

The 6-ft-3, 205-pound Estiwal is a tall and lanky left-handed hitter and thrower with some raw power. Most see him as a future right fielder, thus the Strawberry comparisons. Estiwal has a graceful swing, and scouts like his ability to barrel balls up. Evaluators discuss his improving hit tool when talking about Estiwal’s future. Overall, Estiwal has been praised for his ability to hit in games and hit the ball to all fields. He has also shown some power in games and the ability to drive the ball to the opposite field. Scouts describe Estiwal as an average runner and say his arm might be a tick above average.

That hasn’t happened yet, but the potential is still there. The average age for most players in the Midwest League is 22 or 23 years old, so Sierra being where he’s at right now is a sign of his talent. However, what most people are looking for is production and Sierra has yet to tap into his powerful physique by pummeling baseballs over the wall.

He’s only hit as many as three home runs in a single season, though he’s already at two this year and those were mammoth homers. One hit the Performance Center in South Bend, a good 50 feet beyond the right field wall and up a hill.

When it was announced on June 10 that Sierra would be participating in the home run derby as part of the Midwest League All-Star game festivities, I was taken aback a little bit. Not because he can’t hit home runs, but because his current swing is not designed to hit a lot of them. He’s trying to drive the ball from gap to gap at this point.

His .237 average is not stellar and his 5.7% walk rate is the lowest of his career. Sierra appears to have good pitch recognition skills, so it is surprising that his walk rates have dropped. Still, it’s not uncommon to see such things as players adjust to swing and/or approach changes.

The most important aspect of Sierra’s development is tapping into that power, which he may be able to do if he gets that swing calibrated to produce a little more lift. He looks to be adjusting almost every day, almost on a pitch-by-pitch basis. We’ll really get a good idea of how much he’s improved when he goes through the league a second time in the second half.

We’ve heard many times that development is not linear, and some players take longer than others to put it together. Sierra has all the physical tools to succeed and he has shown that he is not afraid to work hard. He just has to continue making adjustments and hopefully the results will come.

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