The 20-80 scale is a fairly standardized way of evaluating players. Generally a player is given two scores for each category in which they are rated. The first score is how the player currently rates in that particular area, and the second is what their potential is believed to be at their peak.
The scale itself, as best defined, from Kevin Goldstein of Baseball Prospectus:
A score of 50 is major-league average, 60 is above-average (also referred to as “plus”), and 70 is among the best (“plus-plus”). 80 is top of the charts, and not a score that gets thrown around liberally. 80s in any category are rare, and the scoring system is definitely a strong curve that regresses to around 50 at the major league level, but lower as you move down. Very few players have a 50 score or higher for every tool. Just being average across the board is quite an accomplishment.
I actually don’t have a lot to say about this particular topic that hasn’t already been said (and better), so I’ll leave you with some other articles you can read about the topic.
- Saber Scouting’s Scouting Tutorial
- Scout.Com’s 20-80 Scale
- Baseball Examiner’s Article about the 20-80 Scale