Predicting the Power Tool Using Metrics

Former Braves and current Yankees “prospect” Cody Johnson blasted the longest home run I’ve ever seen. In 2008, it came against St. Louis Cardinals pitcher Maikel Cleto (A Mets prospect at the time). Johnson turned on a 95 MPH fastball at the letters, and in turn, seared an “80 power” grade into my mind for eternity. At the time, I wasn’t really concerned about the metrics behind actually producing to the home run equivalent “80 power” (38+ home runs at the Major League level), but neither were scouting contacts. In retrospect, I should have paid more attention as his K%, 34.4%, made it impossible to project elite power from any prospect.

Why? Fangraphs veteran Jeff Zimmerman looked at true “80 power” seasons over the past 38 years and found a sweet spot from a metrics standpoint amongst players accumulating 38+ home run seasons. These include:

FB% = 43%
HR/FB% = 23%
K% = 22%

In Johnson’s case, his 34.4% K% should have raised enormous red flags, as hitters generally strikeout more as they move up levels in an organization. This line of thinking held true as Johnson went on to post a slightly higher strikeout total in high-A, followed by a 43%-plus rate in double-A which has essentially ended the discussion of Johnson as a true prospect and is responsible for his being shipped to the Yankees as a potential reclamation project.

Entering the season, Baseball America’s top-100 included specific tools and their associated grades. For example, the number one prospect in baseball was Bryce Harper, whose power tool was graded as a true-80 on the 20/80 scale. For reference, the full scale is below.

**Thanks to Dave Gershman of for the offense/hitting grades chart**

Look further down the list and Oakland Athletics first baseman Chris Carter ranked as the 91st best prospect in the game with a power tool good enough to earn a “70 grade”. Having scouted Carter in person with Kannapolis, his in-game power made it easy to hang an identical grade on the young slugger. However, the peripherals behind Chris Carter producing 30+ home run seasons at the big league level are murky at best. And if one is unable to envision a navigable path to such lofty home run totals, then is the grade even useful in the first place?

In triple-A, Chris Carter has now accumulated well over 900 plate appearances at the level with a K% of 24-25%. A small sample at the Major League level indicates a strikeout rate above 33% which should somewhat regress to the mean, but may never fall below 27-28% based on this piece on MLE which surmises players strikeout 2.5% to 3.6% more at baseball’s highest level.

Additionally, it’s important to pay passing attention to walk rates. Even though it is generally accepted that higher walk totals lead to better pitch selection and more consistent production as a batter, it does cut into the total number of batted balls to work from. In Carter’s case, I’ll just average his walk rates between what he accumulated in Sacramento this season and his career walk rate in Oakland. That average is an even 10%.

Based on 600 plate appearances, a 10% walk rate and 28% strikeout rate means Chris Carter is unlikely to put a ball in play 228 times. This leaves 372 at bats for which he will actually make contact. For those remaining at bats, let’s see what Jeff Zimmerman’s “Sweet Spot” rates produce in terms of home run production.

With a 43% fly ball percentage, Chris Carter would project to hit 160 balls in the air over the course of a season. If 23% of those balls left the park, his home run total would be 36-37 allowing Carter to exceed his “70 power” projection.

Unfortunately, only 26 qualified players in Major League Baseball this season actually reached a 43% fly ball rate in 2011. Even more damning is the fact only one player (Mike Stanton) has crossed the 23% HR/FB threshold. This brings up a simple, common sense question. Is Chris Carter a player capable of posting FB% and HR/FB% amongst the best in baseball? Whatever sample size we do have points to a resounding no.

And while this line of thinking creates a bit of a sliding scale in terms of a path to power totals based on FB% and HR/FB% both being able to affect a player’s home run totals, Carter achieves his “70 grade” with percentages in the 40% FB and 20% HR/FB range — a far cry from the 50% FB and 8% HR/FB he has posted which would produce just less than 15 home runs over 600 plate appearances (40 grade)

A nearly perfect batted -ball comparison this season would be Cardinals Lance Berkman who has accumulated 31 home runs based on a FB% of 40% and HR/FB of 20%. However, his walk and strikeout totals only count for 31.7% of hit total plate appearances, a full 6.3% less than we can expect from Chris Carter adding nearly 38 additional opportunities to make contact and about three more home runs — a difference of nearly half a grade.

Having scouted Chris Carter early in his career in the South Atlantic League, I find myself pulling for the young first baseman to win the first base job in Oakland outright. However, the more I analyze the numbers behind Carter’s projected power totals, as well as other players with similar skills, the less confident I am in their ever reaching those lofty grade expectations.

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Mike Newman is the Owner/Managing Editor ofROTOscouting, a subscription site focused on baseball scouting, baseball prospects and fantasy baseball. Follow me onTwitter. Likeus on Facebook.Subscribeto my YouTube Channel.

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Does the power scale change? In other words, would 80 power have been higher than 38 home runs in, for example, 1998?


I have the same question.

Isn’t a “50” supposed to be MLB average? Cause the average player doesn’t hit .277 with 18-19 homers. MLB average is actually .255 with 12 HR’s per 500 PA’s.