One of the most important pieces of information we must consider when evaluating a prospect is the player’s age relative to the level at which he is playing. If a player is considerably older than most of his competition (or conversely, if he is much younger than his competition), we must account for that when projecting future performance. If you are someone who generally pays attention to the various minor league systems around baseball, you probably have a feel for what it means to be old or young for a level. For example, a 25-year-old who is tearing up High-A is often less impressive than a 19-year-old who is simply holding his own in the same league. If we merely compared each player’s overall statistics, without considering their ages, we would be improperly assessing their future projections.
That being said, how do we objectively determine the ideal age for a prospect to play at each level? The quick and easy method would be to simply calculate the average age for each minor league. Those numbers are easy to find over at Baseball-Reference. However, these ages are not an ideal reference when we are evaluating prospects, because not every player in minor league baseball is an actual prospect. Many minor leaguers are simply organizational players, guys who have little to no shot at ever playing in a major league game. They are there to fill out minor league rosters, often as bench players or middle relievers. These organizational players are often much older than the legitimate prospects that join them on the diamond. Unfortunately, there is no distinct line between organizational players and prospects. All players are included when these average ages are calculated, and the older non-prospects skew the results toward the older side. As you can see in the link above, the average age of an International League (Triple-A) position player was 26.9 in 2010 (26.6 for pitchers). In reality, if a player is 27-years-old and playing in Triple-A, he most likely is no longer much of a prospect.
In an attempt to find a more relevant connection between age and minor league level, I decided to look at major league performance. I figured the best way to separate prospects from organizational minor leaguers was to only consider players who eventually make an impact at the major league level. So I looked at every position player who accumulated at least 15 Wins Above Replacement (WAR) between 2001 and 2010. That criteria left me with 88 players, from Albert Pujols (80.6 WAR) down to Ian Kinsler (15.7 WAR). Obviously, this is a pretty subjective method, but it accomplishes our fundamental objective of gathering a group of impact major leaguers. Once I had my sample population, I began looking at each player’s minor league career. I recorded the age that each player spent at each minor league level, and calculated the average. I used the player’s age on July 1st as his age for that entire season. I also excluded any stops that did not exceed 100 plate appearances. Here are the results.
| Level | Age | Total Seasons |
| Rookie | 18.1 | 50 |
| Short Season | 19.8 | 33 |
| Low-A | 19.6 | 71 |
| High-A | 20.7 | 80 |
| Double-A | 21.4 | 94 |
| Triple-A | 22.7 | 108 |
As you can see, the results at the lower levels look a bit goofy. The average age of players at short-season ball was actually higher than that at Low-A. Most likely, this is because many of the better prospects skip over the short-season level. I included the number of total seasons to illustrate this. There were only 33 seasons spent at the short-season level among the 88 players in this study. I added the trend line in the graph to try to smooth out this oddity a bit.
If you compare these numbers to the average ages on Baseball-Reference, you can see that our results are much younger. Keep in mind that these are some of the best players of the past decade, so it is understandable that they progressed through the minors more quickly than the majority of prospects do. On average, we are only looking at about three players per team over the past decade, compared to the hundreds of legitimate prospects that have passed through each organization over that same period.
Since this is a Pirates site, let’s apply this information to some of the top prospects in the Bucs’ system. Keep in mind that these results are only pertinent for position players (I may look at pitchers in a future post). Tony Sanchez is entering his age 23 season, and will start the year in Double-A Altoona. That is a couple years older than our average of 21.4. Sanchez was obviously slowed by his fractured jaw last year, so he will be looking to make up for lost time in 2011. Starling Marte is also set to start off in Altoona, in his age 22 season. He is pretty close to our timeline, and will be sitting pretty if he can make a late-season jump to Triple-A. Next up is Andrew Lambo, slated to start the year in Triple-A Indianapolis. Lambo is only 22, so he is actually a bit ahead of schedule. There is plenty of time for him to develop before moving up to Pittsburgh. Chase d’Arnaud struggled a bit in Double-A last season, so he may return to that level to start the year. The 24-year-old would like to move quickly up the chain, as he is already above our average Triple-A age. Jarek Cunningham, 21-years-old, should make the jump to High-A Bradenton this year. Despite missing the 2009 season to a torn ACL, he is still pretty much on schedule. Gorkys Hernandez has stalled a bit at Double-A the past few seasons, but he should start the year in Indianapolis. He is 23 now, so he is in a pretty good spot. 2010 draftee Mel Rojas Jr. spent his professional debut at short season State College, and should spend 2011 at Low-A West Virginia. He will turn 20 in May, so he is pretty close to our timeline.
I will not go through every Pirates prospect, but here is the same graph that is shown above. I added a point for every position player included in the team’s 2011 top 50 prospects, using each player’s 2011 age and expected level to start the season.
