Is your friend a draftee out of HS or college?
Most HS draftees go directly to rookie ball. There they usually get more direction and gives them an opportunity to grow up a little bit, for some being their first time away from home. Rookie ball also, I htink, places that level on drills and some practice, with less importance (or none) on winning.
Most 3-4 year drafted college players go to short season (A) or to join a team that is already in progress (low A). All organizations do things differently mostly depending on their needs, not a players.
One of my son's college friends, at 22 and a senior graduate was sent to rookie ball. He was a lower drafted player (40th something round) 3B and that was where he was needed, or maybe he was sent there because he was not needed anywhere else? They used him as a catcher. I think he remained only one season in pro ball. Another one of my son's friends, also an older college student with degree, was first placed in rookie ball (pitcher) for all of last season. He was our pitching ace, drafted in the top 10 rounds. Now in low A.
Sometimes the organization does not know much about the player's abilities (as he was not highly scouted) so he is placed at a level so he can be evaluated and maybe moved later on. However, most organizations do not move their new drafted players so quickly unless they are high draft choices. I have seen players go through 2 years of rookie ball. I have seen a player begin ss last summer, move to High A second year and just moved to AA, but he was a first round draft choice on the fast track for the organization.
This is a very important question to ask the scout before one decides to sign.
No matter where a player is placed, the goal now is to work hard to get to the next level as quickly as one can.
