Shadowslam (EPK) has already touched on this just a bit, but i would like to provide my theories on the u21 training and why training primaries is important but not always the right path.
Whether people wish to admit it or not, the training path for the u21 and the training path that a trainee might otherwise take for team use are typically no different. When training a Big for the u21, you get driving, handling, and occasionally add some other outside skills, but for the most part you hit some combination of IS, ID, REB, and SB to get that player to a comparable level. The only time one would not build a player to a high combination of IS and ID is lower potential (star and all-star). It's simply a matter of timing and effectiveness of the player that a team wishes to have. Some would rather spend fewer games on training a guy on their secondaries, which would lead them to develop primaries after the age 20 season. This is a double-edged sword, as that guy with great secondaries now will have a long road to actually being good enough to play on the inside.
In reality, the only other time someone might not want to develop a guy's primaries right off the bat is when they wanted to keep salaries lower to make more money. This is true in some ways as you spend less per week, but you are likely winning more games and filling more seats the other way. I trained my players well rounded because i wanted to try and land the #1 pick in the D.III draft while training players, so winning wasn't important and therefore salary wasn't important.
This does not mean that every player should be a cookie cutter design. In previous seasons, we might have had 15-16 players that fit the offense desired. This season, we only really had 8. This is not because of a lack of scouting, this is because of a lack in players properly developed for the u21 team for that offensive scheme (PTB/LI). IF we attempt to follow this design to the end, I think we limit what we can be as a u21 squad. We need to be accepting of those 7 potential guys that may lack rebounding but have other skills that benefit the cause (such as better flow from passing, or higher OD so that they might fit the SF mold), even if our ideals fall in a different player build, otherwise we are a victim to any week where gameshape falls short. Unless we want to do the advertising for the game ourselves rather than hope that BB wants to invest in SEO again, that is a big part of what will help reestablish this team as a power.
Josh