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Surprise, Arizona —— Entering play on Wednesday night, Chicago Cubs outfield prospect Jonathan Sierra is slashing .241/.318/.353/.671 through 30 games (116 at-bats) for the Arizona League‘s AZL Cubs, with five doubles, a triple, two home runs, 11 walks, and 41 strikeouts here in his second season of professional baseball. I observed the supremely athletic 18-year-old outfielder in his August 8 game on the road against the AZL Rangers; below is Baseball Census‘ full Jonathan Sierra scouting report, including video.

Jonathan Sierra Scouting Report — Video

Our video of Chicago Cubs outfield prospect Jonathan Sierra shows his at-bats in that August 8 game against the AZL Rangers at Surprise Recreation Campus in Surprise, Arizona:

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Jonathan Sierra Scouting Report — Notes

Jonathan Sierra is very young, and very raw, but he’s the best athlete I’ve seen thus far in my time in the Arizona League—and it’s really not even close. The Chicago Cubs prospect moves very well, tracks balls well in the outfield, runs easy with long strides, and gets up to top speed quickly and efficiently. He won’t necessarily be a base-stealing burner, I don’t think, but his speed will play as a left-handed hitter and if he develops consistent power, his ability to run the bases will further accentuate itself. He’s a physically strong kid, too, extremely well built relative to his age with a frame enviable by players much older than the teenager. He should still fill out some in the coming years, and his body type will work well with packed-on muscle by his mid-20s.

Tool-wise, even with his above-average speed showing out, Sierra’s best tool right now is his arm. A lefty-throwing right fielder, he has great raw arm strength, gets very good carry on his throws, and is accurate to both cut-off men and bases. His athleticism could find him in center field in spurts over the next few years, but there’s no question he has enough arm strength to play right field and looks like a natural at the position already, taking efficient routes to balls and proving himself to be alert with good situational awareness.

At the plate, Jonathan Sierra is much more of a work in progress, above-average athleticism or not. His physicality and swing mechanics should develop above-average power one day, but he must first learn better pitch recognition and develop better plate coverage and strike zone discipline. He can get rotational in his upper half at the plate, too, pulling off pitches and too often trying to pull the ball with authority. There’s a time and a place for that, but the outside corner is a black hole for him right now and he’s rolling over hittable pitches because of an extreme pull approach so early in his career. He’s a teenager, though; adjustments will have to come as he faces better and better pitchers in the coming years (or adjustments won’t come, and then we’ll know, too).

Long term, I’m loath to project out an 18-year-old kid playing stateside for the first time in the Arizona League, so let’s not have a conversation about whether Jonathan Sierra is an everyday right fielder of the future, or a platoon outfielder, or organizational depth. It’s too soon to tell. What I do know is his athleticism is off the chart, and he carries himself like a much older player. His defensive capabilities are advanced for this level, and will help him add value even while he must adjust at the plate. He looks the part of a prospect and catches your eye with the build of a grown man on a field of 18- and 19-year-old kids. That ultimately means little by way of outcomes, but could bode well for his development if he can put it all together.

All that stuff is good, and makes for an interesting player to scout, but there’s a lot of development to be done here. At present, the Chicago Cubs have a lottery ticket in Jonathan Sierra. Maybe he’ll figure it out, and maybe he won’t, but his athleticism will forever make the outfielder a fascinating one to watch in the coming years. He’ll always flash plus power to his pull side, but the more quickly he can develop a mature, gap-to-gap approach at the plate, the better. Until then, he’s going to strike out a lot in between getting those rare pitches on the inner half of the plate with which he can do damage to right field.


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Bobby DeMuro

Bobby DeMuro is the founder of Baseball Census. A former college and independent league baseball player, he now watches more than 200 games a year working full time for the site. You can follow him on Twitter @BobbyDeMuro for more.

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