Organizational depth is a common phrase used around baseball to describe older minor league players that help fill out Double-A and Triple-A rosters. They could be players with a bit of big league service time or guys that may have been branded as having a ceiling that’s upper-levels-of-the-minors high, but not any higher. Reading utility man KC Serna might be a player categorized in such a way, but that doesn’t impact his goal of continuing to climb upward in the professional ranks.
Another similar term journeyman is something that Serna explains can be a good thing, but not where he plays.