Hi guys! I've heard two sides to this, so I'd like your expert opinion. 

If you draft an 18 year old (like my guy below) whose numbers are good enough to start out in AA or AAA, would you still start him out in RL and make him earn his way up, or would you start him higher in the minors and make his way to the majors quicker? Would you ever start someone out immediately to the majors? I wouldn't do that with this guy, but I'm also curious.

I would start him where ever your best minor league coaching is.  Level doesn't matter as long as he is getting full play time.

Depends on when you expect him to be BL-ready.    If you think he'll be ready at age 20, AA-AAA-BL.    At age 21, LoA/HiA-AA-AAA-BL.

Unless you have good coaching in RL, I'd skip it all together.

I have no hesitation moving guys up from HiA to the majors, if their ratings are good enough. Sometimes I start them in rookie, sometimes in LoA, but don't worry about getting them to AA or AAA before a promotion.

Thanks so much, guys! I appreciate your responses!

Looking at my coaches, AA is definitely the place to start him. AA has my best hitting coach other than the majors.

Hardball Dynasty – Fantasy Baseball Sim Games - Player Profile: Alex Valdes played his first season in RL.   Next two in HiA(I had crappy AA coaching the 2nd season).  A partial in AA and was called up around game 100 this season.   I needed a hitter and didn't have time to fart around with my "plan".   So he didn't get a full season in AA or any time in AAA.   67 AB in, doesn't seem to have hurt him.

Haha! Yeah, he looks like he's doing pretty well! 

There were two points in there:

1.   He didn't naturally progress thru the minors and his development looks just fine.
2.  Make a plan but be flexible.  If you need the guy before you planned to use him, just do it. 

Awesome. Yeah, it's so hard to deviate from a plan, but you gotta do what you gotta do!

seems smart to factor in overall rating and age to dictate where a player should start out. in general, there is a large volume of 58 overall players hanging out in AA, so your player would definitely fit in there, but since he's the minimum age you could start him in high-a for the half season and let him have some fun and obliterate the pitchers there. there's generally not many 18 year olds in high-A.

another concern would be health (for pitchers) and dur (for position players)... without even looking i guessed his dur was something like 60 (actual is 59) so early in his career you'll want to keep him well rested. go to the player settings and leave his "allow rest" checked and set the auto-rest fatigue number to something high like 98. 

sometimes you'll end up with guys that simply don't belong in the minors for very long, like  Hardball Dynasty – Fantasy Baseball Sim Games - Player Profile: Mike Prinz (age 20 on draft day, unusually-high overall rating for his position) so he only spent a few dozen cycles in AA and about a season in AAA and it was time. Also  Hardball Dynasty – Fantasy Baseball Sim Games - Player Profile: Pepe Gregorius was 22 years old 75 overall when I signed him in IFA, and he already qualified defensively so i would have started him immediately in ML but he arrived something like 6 cycles before the service time call-up date so i sent him to AAA for a minute before calling him up. I also used that unexpected opportunity to trade my existing 2B in a package for a young superstar 3B and a very good young SP. 

like mike said, even if you think you have a plan, circumstances can change, so just do it.   Hardball Dynasty – Fantasy Baseball Sim Games - Player Profile: Alex Mota definitely wasn't supposed to be in the ML yet for an entire full season, but my team in that league is sucking and my catchers are killing my lineup and my pitching staff, so i need him now for both offense and defense. he's the best catcher in my organization... kinda like what the Mariners did with Zunino in real life. you gotta do what you gotta do

I'm not so sure I'd use OVR as a guideline.   It's certainly tied to DUR but, if you somewhat manage your minors, you can avoid any fatigue problems.