Sarris: The success rates of Arizona Fall League all-stars

From SABR member Eno Sarris at FanGraphs on November 13, 2013:

Players are sent to the Arizona Fall League for all sorts of reasons. The MLB-owned prospect-laden fall league serves as a domestic winter league, and so teams use it as they wish. But once you are selected as an all-star, an AFL Rising Star, you’ve got a unique stamp of approval, something akin to being an all-star in a league of all-stars. And now that the Rising Stars game has been around since 2006, we have some data to see exactly what that selection means for a prospect.

Some teams send players to Arizona because they were injured during the year and need to build up arm strength, innings pitched, or plate appearances. Some teams send players to try out a new position. Some teams send fast-track prospects from the low minors so that they preview what play in the high minors will look like. Some teams send polished picks straight from the college ranks so that they can skip a level on their way to the bigs. Some teams send prospects they might like to trade so that they might look better to future trade partners after some time in the offensive-friendly league. Most teams send players that face the Rule 5 draft if they aren’t moved to the forty-man roster.


So how do they stack up in terms of major league success?

Using the Rising Stars rosters between 2006 (the first iteration of the game) and 2011 (in order to give prospects some time to hit the majors), I set out to answer that question. “Success” was defined as 1.5 WAR per 600 plate appearances or 150 innings pitched since the MLB samples for some of these players were small. Given all the disparate reasons a player can be sent to the AFL, the statistical outcomes from the data set ranged from expected to surprising.

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Originally published: November 13, 2013. Last Updated: November 13, 2013.