Often when the discussion about major league roster construction comes up, it affects how a prospect will fit into an individual organization. However, the overall construction of major league rosters dramatically affects how prospects are evaluated. Before talking about it affects certain types of hitters and pitchers in the system, we need to look at how the current major league roster is assembled and why it is assembled that way.
The first thing that is a given in today’s game is that there are 13 (14 in the AL) starter spots locked up on a roster. If any of the 8 position players are in a platoon, one of them is accounted here and the other must fit into the bench construction we will get to later. As for major league rotations, if anything they are growing past a 5 man rotation rather than shrinking the number of starting pitchers on a roster.
For some reason baseball teams have decided that the ideal bullpen is 7 guys. This decision has shortened bench and lengthened the bullpen. The bullpen itself has some “needed” pieces, in reality the “closer” and “setup” roles can be replaced with the need for two high leverage relievers.
1 Setup Reliever
1 Long Man
1 LH Specialist
That leaves us with 3 spots to fill, in general this requires at least one more LH pitcher if none of your Closer, Setup, or Long Man are lefties. If you have at least one more LHP you are likely good, if you have more than there may be a spot for a RH specialist. To add to this other specialist you have another “middle” reliever who may get the label of “7th inning guy” if he is good enough, but the bullpen normally needs to get at least 3 innings of work.
This leaves the 7th guy in the bullpen, who works maybe once a week in mop up situations. Overall the marginal value of this last reliever is low, unless the manager plays matchups a ton. But the reality is that managers like having that last man in the bullpen for long games. More than that more and more relievers are unable to go multiple innings and more are being used for a single batter, which calls for an emergency reliever.
Because of 7 man bullpens, the major league bench is either 4 or 5 players. There are three necessary roles; a backup catcher, an infielder who can play 2B/SS/#B, and an outfielder who can play CF. Because of the demands of these tough defensive positions the offense is marginal for these players. The backup catcher is essentially irrelevant as a pinch hitter, because of the risk of the primary catcher being injured later in the game.
The last two spots tend to be either the platoon partner of a starter or primary pinch hitter. Unless either of your other usable bench players has some pop in their bat you want your two bench bats (often an infielder and outfielder) to be RH and LH. This ends up creating a very specific list of needs. In the end this marginalizes players without pop, who can’t play SS or CF, as well as positionless mashers. American League teams have a little more flexibility since they don’t have to worry as much about pinch hitting, but in the National League this roster crunch stunts certain styles of hitters.