Prime9:
I would say that you have a great attitude and staying positive is important as a lot can happen over a college season. A lot of these things may include injuries, extended slumps by starters, off field issues, pinch hitting in a key spot, and many more opportunities to get his time.
Some may not see it this way, but I see a positive in that the expectation bar has not been raised high for those 5 freshmen by the coach. Perhaps the coach wants to see who wants it bad enough to prove his statement to them wrong, who knows. He knows what a grind the season is and that several things change. It is rare that the way the season starts is how it finishes, I will tell you that.
All I can suggest is that your son work harder than anyone on the team. Take extra BP and extra infield work. Volunteer for grunt work, and be seen as a team player. It will get noticed.