Back in the late '90s, the so-called "Trinity" at shortstop -- Nomar Garciaparra, Derek Jeter and Alex Rodriguez -- provided the most memorable concentration of young talent at a position since Willie Mays, Mickey Mantle and Duke Snider graced center field in the '50s. They also heralded a golden age for shortstops cut more from the Cal Ripken cloth (big, athletic and offense-minded) than the Ozzie Smith one (small and speedy, with an emphasis on defensive skill). These days, the class of elite shortstops is much thinner: Hanley Ramirez and Jose Reyes might be Trinity-level talents, but from there is a sizable step down to the likes of J.J. Hardy and Troy Tulowitzki.
Instead, the high-end young talent appears to be concentrated at catcher and center field. One way to illustrate this is via PECOTA's Upside scores. While primarily used for assessing prospects -- any player above 100 is an excellent prospect, with a strong chance of a long, star-caliber career, and prospects above 50 generally still have solid shots at stardom -- the scores are handy for aggregating future contributions for all players along our forecasting system's six-year horizon. Upside credits players only for performance above league average at their position, and includes defense as well as offense. Among a player's top comparables, if one performed better than average, then twice his number of runs above average are counted toward his Upside. If he was below average in the minors, or pounding sand somewhere else, his performance is counted as zero.