Center fielder Jason Martin was the second-youngest player on the 2014 Greeneville Astros squad, behind only shortstop Kristian Trompiz (Martin edges out right-hander Juan Santos by less than a week). Yet, his 125 wRC+ easily led the team among players who had 150 or more plate appearances. Martin - whose offense isn't even his primary calling card - forced a promotion to Tri-City of the short season New York-Penn League, where he was three years younger than the league-average age.
Boasting a .274/.363/.415 slash line, Martin's time in Greeneville in 2014 outshines quite a few other recent eighteen-year-olds who played in domestic rookie leagues, some of whom are considered better prospects.
This led me to ponder the question: Where does Martin's 2014 season rank among the best-ever by an eighteen-year-old in Greeneville?
The Astros have fielded a team in Greeneville every year since 2004, when Tim Bogar managed the team - led by another eighteen-year-old standout named Mitch Einertson, who set the league record for home runs and won the MVP award that season - to an Appalachian League title.
Since that year, seventeen former G-Stros have gone on to play in the major leagues: Fernando Abad, Jose Altuve, Brandon Barnes, Jimmy Barthmaier, Jose Cisnero, Jorge De Leon, Michael Foltynewicz, Victor Garate, Samuel Gervacio, J.C. Gutierrez, Jordan Lyles, J.D. Martinez, David Martinez, Troy Patton, Felipe Paulino, J.R. Towles, and Henry Villar.
In that time, a total of nineteen age-18 players have stepped into the batters' box for the team, as well as four seventeen-year-olds (Carlos Correa, Jay Austin, Delino DeShields, and Ariel Ovando). Five of them (Einertson in 2004; Koby Clemens, Ralph Henriquez, Allen Langdon, and Timothy Johnson in 2006) were before the Fangraphs era, so it's harder to parse them out.
Even without available advanced metrics, it's pretty clear that with a 1.104 OPS, 24 home runs, 67 RBI (more than any other two players on the list put together), and 53 runs scored in 227 at-bats, Einertson's 2004 season set the gold standard for eighteen-year-olds in Greeneville.
After such a promising start, Einertson - a fifth-rounder in 2004 who could play all three outfield positions - saw his career stall out when he hit Lexington. Just as it seemed he may be back on track, a fifty-game suspension cut his 2009 season short. To avoid serving the remaining twenty games in 2010, he opted to go the independent-ball route, where again he started strong and eventually flamed out. He quietly retired after the 2013 season at the age of twenty-seven.
Among the 17- and 18-year-olds who have played in Greeneville since 2007, Carlos Correa's 2012 stands head-and-shoulders above the rest. With a ridiculous 183 wRC+, 1.050 OPS, and .229 ISO, it would take an Einertsonian effort to topple Correa's age-17 season. However, Correa put those numbers up over just 41 plate appearances, as he played the majority of that season in the safe(r) confines of the Gulf Coast League.
Filtering out players with fewer than 100 plate appearances, we come up with this:
The names on this list alone should be a giant "Not so fast, my friend" for anyone trying to extrapolate age-eighteen seasons in rookie ball to future success as a prospect. We see Martin here, flanked by Jio Mier and Ariel Ovando, both once-touted prospects who have become afterthoughts, at best. The only other player above 100 wRC+ is All-Star second baseman Jose Altuve.
Martin also gets no added benefit from his defensive reputation. Although he is a well-regarded fielder, so were Mier and (to a lesser extent) Ovando during their age-18 seasons.
If Martin has an advantage, it's in his plate discipline. He limited his strikeouts as well as anyone on this list, and his 0.80 BB/K easily out-paces the field. His isolated power is not as far behind the others as one might imagine, and he also went just 8-for-14 in steal attempts, despite having a reputation as a very good baserunner and stolen base threat. These are areas where improvement can be reasonably expected.
He may also have the advantage of being in a much better-stocked system than either Mier or Einertson, both of whom had a lot of expectations put on their shoulders. In most years, Martin's 2014 season would earn him serious buzz for top-prospect rankings. But this offseason, his name is likely to barely scratch the also-ran category.
It's safe to say that in 2014, Martin very quietly put together one of the best seasons an eighteen-year-old has ever put together for the Greeneville Astros, and it seems likely that he'll be challenged with a full-season assignment in 2015.
Whether the remainder of his career goes the way of Mitch Einertson and Jio Mier or the way of Jose Altuve is, of course, still to be decided.