Rookie Ball Prospect Monthly Roundup

Travis Sherer breaks down the highlights and lowlights of the prospects in the Midwest and South Atlantic Leagues of Single-A.

Rookie ball is a funny thing and a bit of a roulette wheel from an analysis standpoint. Most of the time, you’re looking at the rawest of the raw prospects. In fact, the average age of a player in Rookie ball is 19 years old. In addition, limited sample size is a key consideration. At the time of this writing, most batters have under 20 AB. It leaves you wondering if the talent displayed is legit or if they are simply on a hot streak and/or playing against mediocre competition. More often than not, reports are based on box scores and varying eye witness accounts because, well, the newspaper industry has gone the way of the dinosaur and most writers are not covering games in Danville, Burlington, Missoula, or Idaho Falls.

Still, this is where most aggressive dynasty players start buying in early. So let’s take a look at a few hot hitters from throughout the Rookie league.


Filters and Stats Used



  1. Did not consider pitchers yet. Too small of a sample.
  2. Did not consider players over the age of 20.
    1. I do not care if you’re 24 and beating up on teenagers.
  3. Removed any players under 20 AB.
    1. Too small of a sample inside of an already small sample.

Stats Used

  1. Plate Appearance (PA): As I mentioned, sample size is minuscule at this point. Current average PA is under 20.
  2. wRC+: How good is the contact they’re making?
    1. If they’re a doubles machine, color me interested.
  3. BB-K%: How well can they see the ball?
    1. Is a player striking out at an alarming rate or do they have a wildly high walk rate?
  4. SwStrk%: How bad are they whiffing?
    1. Indication of batters eye and ability to hit breaking balls.
  5. Pitches/PA
    1. If they’re striking out a lot, but they’re seeing a lot of pitches, I’m not as alarmed and they may just be overly patient and/or working counts

Composite with Filter (as of 7/1)

PA wRC+ BB-K% SwStrk% Pitches/PA
43.4 99 -16.2% 22% 2.73



Bryce Ball, 1B, Age: 20, Atlanta Braves


PA wRC+ BB-K% SwStrk% Pitches/PA
42 248 -4.8% 6.4% 3.7


Ball comes in with the best wRC+ of the group and one of the best pitches per plate appearance in Rookie ball and has been mashing since the start of the season. A 24th round pick out of college, Ball was performing very well in college to the tune of a 1.057 OPS and a near 1:1 BB:K ratio. Not to mention the swinging strike rate is darn near microscopic for this league. Despite his first base only status, he’s one to keep an eye on.


Gregory Guerrero, 2B, Age: 20, New York Mets


PA wRC+ BB-K% SwStrk% Pitches/PA
47 159 4.3 12.6 4.4


Guerrero, the other guy besides Andres Gimenez signed in during the 2015 J2 signings. At the time, he was ranked 17th in the MLB’s top J2 prospects and is the nephew of former major leaguer Vladimir Guerrero, cousin of Vladimir Guerrero Jr.

Guerrero was probably forgotten by a majority of dynasty players after a rough 2017 rookie ball debut and a 2018 season lost to injury. However, his 2019 season is off with a bang. Guerrero is rocking one of the best BB% across rookie ball and displaying a strong level of patience with his approach to the plate. There is some speed on the base paths and he has shown some flashes of power too. While he’s been hitless in his last five games, I would keep an eye on him and be ready to pounce with a late-round flyer in leagues 16 teams or deeper.


Liover Peguero, SS, Age: 18, Arizona Diamondbacks


PA wRC+ BB-K% SwStrk% Pitches/PA
56 177 -14.3 8.3 3.6


Another J2 prospect signed in 2017, Peguero has been a star for Missoula. While he’s not one for power, the speed plays up here as exemplified by six doubles in 56 at bats which is good enough for second best among all players in Rookie ball. The K% isn’t quite where I would want it, but his patient approach and quick hands make it seem as if he has a natural ability to hit.  If he keeps this up, expect a promotion before the end of the year.

(Photo by Cliff Welch/Icon Sportswire)

Adam Lawler

Fun dad. Generally tired. Follow me @TheStatcastEra.

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