This article is part of our Farm Futures series.
The bottom of the defensive spectrum is a dangerous place to be. The occasional prospect gets developed as a first baseman and profiles as a plus defender there, but most of the players who end up at first base or DH are there because they aren't good enough defensively to play anywhere else, yet their offensive production is so appealing that their team finds a spot for them.
The rule for first-base prospects is that they need to hit. They need to always hit, at every level of the minors. That doesn't mean being five or 10 percent better than league average. It means being at least 20 or 30 percent better if the player is young for the level, and at least 40 or 50 percent better if the player is at an age-appropriate level. This is not a place to preach patience. Often, these players come with a decent amount of swing-and-miss, which is fine as long as they also walk a lot. The best first-base prospects walk almost as much as they strike out.
I often reference when a player who may end up at first base bats and throws right-handed, because it puts even more pressure on the player's offensive output. Offensively, teams would prefer their first baseman to have the platoon advantage against righties, and defensively, left-handed first basemen are better suited to fielding balls hit in the hole between first and second, making throws to second or third, and holding runners on base. That's