I posted a similar question in the forums before, this one is slightly different.

How do you guys go about developing a low durability position player? Say I have a 19 or 20 year old prospect in LoA. His durability is less than 50 currently, and projects to 65-70.

Do you allow him to get as many ABs in the minors as possible, even if his energy% dips under 90, or maybe even under 80? If you do rest him, how do you do it? Do you place him on inactive list for a few games until he's back at 100 or some other way?

I platoon players once they hit under 100. When a player that goes under 100%, all of his ratings are negatively effected even ones that involve injuries.

I try to never play a prospect ( a good ML quality one) under 90 , under 95 if possible. I have a player like you are describing I try to have a high durability player to take as many AB's as necasary to keep the prospect playing but not below 90-95 %, once the prospect gets fatigued I just rest him if have room on the bench, if not I add him to the inactives, until he is back at 100% for awhile , so he can play a bunch of games in a row at full speed

If he plays a position where I care about his defensive development, I'll bat him near the bottom of the lineup so that he'll get more innings defensively per AB. And I'll set up a defensive replacement to sub for him in the 7th inning as often as possible to increase the number of games he can start.

pb15 makes a great point - the lineup is a place where you can really help your own low DUR guys. Batting 8th/9th means 1 less AB per game, ~20 per development cycle if you use the defensive replacements aggressively. If I have two low DUR prospects, I will bat them back-to-back in the 8-9 spots and carry defensive replacements at their position, plus a SS to protect the rest of the team.