As others have said, the tricky part of this is when talent levels are nearly the same between under/upperclassmen. THEN who should play?
In some cases, where the team is clearly in a rebuilding year (i.e. only a few seniors this year, not much depth at pitching), some coaches would prefer to get an underclassman ready for future years. That's still a tough pill for a senior or junior to swallow, when they and their whole team can see that a sophomore didn't clearly outplay them in the preseason, yet come game 1 of the regular season, most of the infielders find themselves juggled into new positions to accommodate the shortstop of the future.
To make it even harder to buy into this is the fact that the very same senior who "lost" his SS spot was brought up to V as a sophomore and played there the past two years, only to watch the NEW flavor of the day get his shot now.
On top of that, what if the team hasn't had a winning season in the past decade? At what point does the coach just realize "My constant search for the next great stud isn't panning out, and meanwhile, I'm not really showing much loyalty to my upperclassmen (again, ONLY if they're still equal in talent to underclassman), so maybe I should get over this whole 'build for the future' stuff and maybe focus a bit more on what I have right now"???
FWIW, no, MY son isn't the senior SS who was pushed aside this year for the soph. But my son and the senior played most of the preseason games at SS and most people thought that was the competition for SS. Then, all of a sudden, the practice before the final preseason game, the switch was made, and the soph has been the SS ever since. On top of that, he made a couple errors in that preseason game, so this was a real shock.
Now I must admit that the soph so far is playing very well at SS and is also leading the team in batting average (through 4 games and 13 plate appearances that include 2 HBP and a walk, which isn't enough ABs yet to draw any conclusions). So maybe this coach IS a genius and just saw something at practices that we didn't? Or maybe over another 10-15 games, he won't continue this pace?
This can create an air in the dugout in which upperclassmen are looking over their shoulder too much. I understand that to a certain degree this is always the case. But when a team sees their starting senior SS for the past two years as well as the starting JV/freshman SS the past two years BOTH pushed aside before even a regular season game has been played, it just doesn't seem like much of a morale builder. Now, if the coach really has his eye on the NEXT couple years, then it starts to make sense (though I still disagree) - especially if, as the season progresses, the team gets in a deep hole before mid-season, the coach starts to "give" more upperclassmen positions to underclassmen. That'd be a shame if the older kids haven't actually "lost" their spots. Why punish them because the team lacks pitching depth and won't win a lot?
It's just tough to watch upperclassmen be pushed aside when they haven't clearly lost their spots. This isn't pro baseball folks, we're still dealing w/ KIDS.
My 2 cents.