The Minor Leagues
Four full season levels below the majors, and the ladder every player except a handful has climbed.
What it actually is. Each club owns a farm system: Triple-A, Double-A, High-A and Single-A, plus complex level rookie ball. Players are assigned rather than signed, and a club may promote or demote them freely subject to option rules. Triple-A is the last stop and Double-A is generally where the best prospects are, because that is where the jump in quality is largest.
What somebody who knows the game gets out of it. Double-A is the level scouts care about most and it is worth knowing why. Triple-A rosters are half prospects and half experienced players in reserve, so performing there proves less than it looks, whereas Double-A is where a young player faces genuine breaking balls and command for the first time. A prospect who handles Double-A at 21 is a different kind of prospect from one who dominates Triple-A at 25.
The numbers worth knowing. The affiliated minors were cut from about 160 clubs to 120 in 2021. A typical prospect spends three to five years in the system. Triple-A seasons run about 150 games.
What people get wrong about it. Minor league statistics need context that major league ones do not, because the leagues have wildly different run environments and the player ages vary enormously. Age relative to level is the single most useful piece of context: a 20 year old holding his own in Double-A is a better sign than a 24 year old dominating it.
At Little League and travel ball. The minor league ladder is why the Batter's Eye rank ladder is built the way it is, running from Rookie through College Baseball and up. It is the sport's own way of describing progression, and it maps onto learning the game better than a generic points system does.
Batter's Eye: look up anything in baseball