I have the #1 pick from last seasons draft of my team who should be a great 2B, but he has a low DUR and his energy is down to 95% after 50 games.  He is in LoA this year so I'm not concerned with his performance really, but want to do my best to maximize his improvement.  So should I just play him everyday and let his energy keep falling or should I rest him and try to keep his energy close to 100%???  What is the best strategy for development??  Any advice would be appreciated, thanks.

I've found, thru trial and error, that players SEEM to get injured more frequently under 98%.   Others will play them non-stop.  

IOW, you'll probably get a bunch of different responses.

thanks mike.

does a minor leaguer develop more/less based on how many at bats he gets?  so if i wanted to risk it would i get more development out of him by playing him more, as long as he doesnt get hurt?

That's also a disputed topic.   I think more AB = quicker development.    Others disagree.    But, if a player doesn't play, he won't develop so I'm not sure why they disagree.   Although I do think there is a limit to max development per season. 

Personally, I check my minor league line-ups once a week.  Anyone below 100% is deactivated for the next week. 

I have a low DUR prospect who only played in 95 games last year (~350 ABs) and he improved 12 points overall including 10-12 in most of the key skill areas.  I believe development is tied to how much a guy plays, but I don't know that the difference is enough to make it worth the added risk of him suffering a major set back.

I inactivate my position prospects when they drop below 97%.  Reactivate them when they're back up to 100%.

For pitchers, I try not to let anybody go if they're not 100%.

Here is a really good pitching example. This is a RP who threw 270 innings in season 20, when he should have only thrown 100. If you look, you'll see his season 20 developement is worse than his season 19 or season 21 dev.
 Hardball Dynasty – Fantasy Baseball Sim Games - Player Profile: Ivan Chavez

I've been dealing with a bunch of position players with low durability fatiguing earlier in the season, i just keep them at 98% autorest and they are basically playing every other day. I want to play them as much as possible, but refuse to let them get below 95% for injury purposes. Sometimes, at the end of the season I'll let them play the final 8-10 games or so regardless of fatigue to squeeze the last bit of improvement out of them.

I also think some guys are just going to reach projections much faster. Hardball Dynasty – Fantasy Baseball Sim Games - Player Profile: Jimmy Fox is my prime example-- drafted him at 52 overall, he's in just his third season now and already jumped to 76 overall. His durability sucks, and he's progressed that much playing just 76 games in rookie ball, 95 games in High A, and 78 so far in AA. His makeup is also great