Talk to any prospect junkie and he'll tell you that age versus level is probably the best indicator of future big-league success. Every statistic a minor leaguer accumulates must be viewed through the paradigm of age versus level. Yet, for some reason, I find myself almost completely disregarding age versus level once a player reaches the major leagues and accumulates some service time.
Starlin Castro managed to hit .300 as a 20-year old for the Chicago Cubs in 2010 and then followed it up with a .307 average in 2011. Entering his age-22 season, a season in which most shortstops would be lucky to make their major league début, I've basically pencilled Castro in to repeat his 2011 line. Sure, he'll get a little better and maybe he'll develop a smidgen more power, but I've basically got him chalked down for a .300/.345/.440 season or almost no progression.
I haven't the faintest idea.
Had Castro showed the power growth while maintaining his average in the minor leagues, I'd be predicting big things, but I have a hard time extrapolating major league data along the typical ageing curve. Castro should continue to improve for at least a few more years before reaching his peak, but I cannot bring myself to buy into this improvement on Draft Day.
What about Giancarlo Cruz Michael Stanton?
Again, I'm left assuming that he'll probably continue doing exactly what he's doing, even though every piece of mathematical evidence suggests that he'll basically improve in all facets as a 22-year old.
Stanton hit 34 HR and posted a .262/.356/.537 triple-slash, and rather than progress that along the ageing curve, I'm simply sitting here thinking, "ehhh, that's probably the kind of player he'll be."
I'm not sure if I'm hedging my long-term bets by assuming that Stanton will remain essentially stagnant for the entirety of his peak, but I feel like it's a leap of faith to predict gradual improvement for the next three or so years.
Once Stanton posted a couple great seasons, I decided that was Mike Stanton. As a contrast though, I have yet to declare Jason Heyward as Jason Heyward. Heyward and Stanton are about the same age and have played roughly the same amount of games. Yet, I have absolutely no problem predicting Heyward taking huge strides in 2012.
I'm not sure if it's ego on my part or just the mathematical certainty that each progressive step beyond the average is exponentially more difficult to achieve, but it's something. On one hand, I assume that every player will reach (and not exceed) the potential I predicted exactly. Stanton and Castro have reached that potential while Heyward hasn't. On the other hand, statistically speaking, it's far easier for Heyward to take the step from good to very good than it is for Castro and Stanton to make the jump from very good to superstars.
If I viewed fantasy baseball like a video-game, I'd absolutely view Stanton and Castro as high-potential players that'd continue to improve throughout their lifetime contracts signed with my made-up video-game team. But for whatever reason, I just can't do that.