Minors To The Majors: Hitter Prospect Grades (Part 1)

Today it starts. I am going to try to find an easier way to take current prospect evaluations and turn them into usable information for fantasy owners. Since none of the prospect information is far from perfect, the following will be an imperfect science, but hopefully, some of the prospect guesswork can be removed. The hope is to eventually see a prospect’s grade and/or ranking and have an idea of what type of production to expect from the player. Additionally, I plan on having a method of taking prospect grades and comparing it to present major leaguers.

From the little work I have done, I find it is so much easier to work with hitters versus the pitchers. I am going to start with them for a couple of weeks getting a decent groundwork done with them. When I get to the pitchers, the work is going to be a little slower moving as I translate pitch grades to a players value.

I want to go over is the basic prospect information I will use. The first bit of data is the20-80 scale for individual grades and overall grades discussed here by Kiley McDaniel. After talking to several people in the scouting profession including our own Eric Longenhagen, the system and scales are the ones commonly used. So for reference, here is basic chart:

Hitting Prospect Grading Scale
Overall Tool Is Called Batting Avg Homers RHH to 1B LHH to 1B 60 Yd Run Hitter WAR
80 80 0.32 40 4 3.9 6.3 Top 1-2 7
75 0.31 35-40 4.05 3.95 6.4 Top 2-3 6
70 Plus Plus 0.3 30-35 4.1 4 6.5 Top 5 5
65 0.29 27-30 4.15 4.05 6.6 All-Star 4
60 Plus 0.28 23-27 4.2 4.1 6.7 Plus 3
55 Above Avg 0.27 19-22 4.25 4.15 6.8 Above Avg 2.5
50 Avg 0.26 15-18 4.3 4.2 6.9-7.0 Avg Regular 2
45 Below Avg 0.25 12-15 4.35 4.25 7.1 Platoon/Util 1.5
40 0.24 8-12 4.4 4.3 7.2 Bench 1
35 0.23 5-8 4.45 4.35 7.3 Emergency Call-Up 0
30 0.22 3-5 4.5 4.4 7.4 Organizational -1


The first item to consider, if you only have an overall prospect grade like available here or in the team pages of the Baseball America handbook, just match up the Overall grade and the other values. This is a start, but an owner should look harder has the type of player is not know. With MLB.com giving grades for each team’s top 30, they will likely have most of the top prospects’ grades.

Normally, hitters are given grades in five categories, Bat, Power, Speed, Field, and Glove. Additionally, the grades usually given are future grades, so make sure when looking at scouting reports, look for future, not current marks.

The next item I will do is to put some actual MLB player comparables to the grades. Two of the categories are easy to translate to current players, Power and Bat as they have an exact range. My first challenge was to figure out the other three.

With Speed, I created a comparison of recent prospect who had prospect speed grades and their actual major league Speed Scores. Once I go the information, I ended up with the following groupings.

Speed Score to Speed Grade Conversion
Speed Score Speed Grade
>9.1 80
8.4 to 9.1 75
7.6 to 8.4 70
6.9 to 7.6 65
6.1 to 6.9 60
5.4 to 6.1 55
4.7 to 5.4 50
3.9 to 4.7 45
2.4 to 3.9 40
1.7 to 2.4 35
< 1.7 30

For defense, I used a player’s defensive WAR component. An average defender has a grade of 0 which is the same as a 50 grade. I had to fudge the numbers just a bit (e.g.making average 0 to 4 instead of -2 to 2) to get a decent bell-shaped distribution curve.

WAR’s Defensive Value to Glove Grade Conversion
WAR’s Defensive Value Glove Grade
>22 80
20 to 22 75
16 to 20 70
12 to 16 65
8 to 12 60
4 to 8 55
0 to 4 50
-4 to 0 45
-8 to -4 40
-12 to -8 35
< -12  30

I understand that 99.9% of all fantasy leagues have no defensive component but a player’s defense is a major factor is the player makes it to the majors or not.

The final prospect grade is Arm. After looking over several methods like using WAR’s Arm component, I decided to just completely ignore it for now. The major issue was that first basemen all have Arm grades around 0 since they throw very little while outfield arms vary greatly. I am sure most of the bad outfielders have a better arms than the first basemen. Now, the Arm grade is still a factor in determining the player’s position since any below average score may mean the player is destined to play on the right side of the infield.

Converting Prospect Grades to WAR Values

I completely understand Wins Above Replacement and fantasy evaluations for major leaguers aren’t perfect comparisons. The deal is that prospects don’t have a major league job yet and we need to know if they will in the future. If a person has just the prospect’s overall grade, they can start with the WAR values from the Grades tables. I like to take it a step future and use the individual grades to create an overall Prospect WAR projection and use the individual grades for fantasy purposes.

For this analysis, I took the MLB players (min 300 PA) and gave them grades using the above criteria (link) and then ran a linear regression on the four grades and a plate appearance adjusted WAR value. I ended up with the following ratios and simplified ratios listed second.

Hit: 44.7% Power: 17.6 % Speed: 11.3 % Glove: 26.4%

R-squared = .70

Hit: 45% Power: 20 % Speed: 10% Glove: 25%

R-squared = .69

The simplified grade is close enough to the original one and included in the spreadsheet linked above.

So now we have a better idea of who is going to make it to the majors but which skills are the most important for fantasy production. To take the final step, I took the MLB player’s Bat, Power, and Speed scores and then compared them to the final end-of-season values I previously found (link to process). At this point, a person may have to adjust the value just a bit depending on league rules such as using OBP instead of AVG or sixth category like OPS.

First, I ran a correlation of just WAR to the fantasy and came up with an R-Squared of 0.42. Some correlation, but as expected the real life and fantasy evaluations don’t exactly line up. Now taking the three values and correlating them with the overall fantasy value, I end up with an r-squared of .67 with the following weightings:

Fantasy Prospect Grade = 0.292 * Hit Grade + 0.406 * Power Grade + 0.302 * Speed Grade

I am not even going to run the correlation if the values get rounded to the 30% Hit, 40% Power, 30% Speed as the above values are almost there right now. In the past, I have always used 40% Bat, 40% Power, 20% Speed for the weighting, but it seems power, and the Runs and RBIs which come with it, are more valuable than average. Also, a nice speed rating can be huge in today’s stolen base environment.

I am calling the process done for today. The prospect grading scale I use has been put out to scrutinized. Additionally, how this scale relates to major league hitters has been calculated. I think the information above is far from a finished product and I expect to come back and adjust it in the future. For next week I will start looking at some hitting prospects and see how they compare to the major league players.

Jeff, one of the authors of the fantasy baseball guide,The Process, writes for RotoGraphs, The Hardball Times, Rotowire, Baseball America, and BaseballHQ. He has been nominated for two SABR Analytics Research Award for Contemporary Analysis and won it in 2013 in tandem with Bill Petti. He has won three FSWA Awards including on for his MASH series. In his first two seasons in Tout Wars, he's won the H2H league and mixed auction league. Follow him on Twitter @jeffwzimmerman.

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Jeff: great work! Unfortunately, two of the three keeper leagues I play in are points leagues. The deductions for getting caught (1.5) are almost as great as the points awarded (2.0) for steals, so speed matters less in these particular leagues unless you have a really great base stealer.
I’m not sure how I’d make the weighting adjustment but one complication for one of the pts.leagues is that we are awarded points for double plays turned and outfield assists, as well as deductions for errors, so this is a league where defense actually matters.
Great read regardless. Thanks!