I've always been under the impression that 21 is age appropriate for Low A, Short Season - 20/19, Rookie - 19/18 and so on. And by age appropriate I mean that is the age of a majority of the players at that level. If you are a top prospect you're probably a year or two ahead of that pace. I'm curious what other people think and why. Thanks. According to BA, the median age for the FSL in 2012 was 23 years old. See: http://yourprospectsucks.tumblr.com/post/24623508386/the-basics-of-minor-league-baseball Also, according to Minor League Central, there are only 13 batters under the age of 21 currently in the FSL. Dustin Geiger is the 26th youngest player in the entire league. http://minorleaguecentral.com/leaderboard?lid%5B%5D=123&y=2013&split=200&amod=%3C%3D&age=99&time=0&type=batter&table=0 According to BR, the average batter age in the FSL is 22.8. And according to them, Geiger is the 32nd, with regards to age, of hitters with an AB. This may be a bit dated, but helpful to this discussion: http://www.fangraphs.com/blogs/minor-league-leaderboard-context/