Seems like there are many opinions on this topic but I think its all relative to the school, the team, the coach and the player(s) in question. Last year, in his first season, our school's new head coach decided to start a freshman on varsity for the first time in school history. His theory was if he was going to make varsity, he was going to play. This did not sit well with anyone in or outside of the program. This had nothing to do with the kid's talent (IMO, maybe not worthy of immediate play at the varsity level, but definitely should have moved up sometime later in the season), but everything to do with the player's maturity and game knowledge.
To the freshman player's credit, he played very well. Unfortunately his immaturity did kick in and his arrogance and "me first attitude" that all of knew would be his Achilles heel, took over. It seems the freshman felt his on-field performance allowed him the luxury of having a "voice" in the dugout/locker room. The kind of role that traditionally (and rightly so) is taken on by upperclassmen. My son alluded to me that "some chairs and fists were thrown on several occasions". Names of plaintiffs and defendants were withheld. Team chemistry was non-existent for 2/3rd of the season and a team returning 7 seniors (5 of which were headed to D1 schools) started 2-10, finished strong but did not make the playoffs for the first time in 10 years.
So, no sweat off that freshman's back because he has three more years to return to the playoffs, right? With five NLI signed Division 1 senior players (two pitchers) and three or four juniors and sophomores headed in that direction hoping to make a strong run in states, how important do you think it is to play an untested freshman immediately when there is so much time to work with? You have a group of guys with at least one season playing with one another, who know each other, have built somewhat of a trust and bond with one another, and rather than slowly introduce a new element to that system, you cause an explosion. Was important enough to talk to your seniors about it? New coach vs four yr players at well respected private school.
We had an anomaly last year in our league last year (considered one the top 2 in CA) where we had 7 freshman starters on the seven teams in our league. One team started 3, another two, one team had one and our team started one. They all had great seasons in games during outside of league play. Keep in mind, coaches notoriously keep the pressure off because games are meaningless counting towards playoffs. Plus, they are not always playing powerhouse teams either. As soon as inter-league games started (keep in mind every team except two in this league had 3-5 Div 1 commits), freshman player batting averages dropped by 43%. In the field, error percentage rose by 56%. The only shining spot was a freshman pitcher (already committed to power 5 school) was spectacular. He led the league with 10 wins and a 1.21 era. Came with a price though. He threw over 1000 pitches. Remember, still a freshman.
So, when I say it all depends on the situation you really have to put things in perspective. Is it worth it if there are options for the player? Are you taking the player away from his peer group at a time when he may need that time for mental growth? Is he ready for the grind? Do the coaches have the time it takes to groom/assist/even protect the freshman player? Is he ready to step up when it really means something? It just depends...