On November 19th, Fangraphs posted an article entitled “The Slow Decline of Speedy Outfielders.” It is worth the full read, but here are some snippets. The article should help alleviate concerns about a steep decline of Ellsbury’s speed-based skills.

There’s a belief among some that speed-and-defense players like Ellsbury are bad bets after they turn 30, since a large chunk of their value is tied to what they can do with their legs, and speed peaks earlier than other skills. However, there’s also data that shows that faster players actually age better than most other player types. Instead of just trying to show you what the aging curves say, though, I figured showing how similar players to Ellsbury actually did might be more appealing.

Without copying & pasting the entire methodology, Fangraphs compared what Ellsbury did between ages 27-29 and found 12 retired players over the last 30 years with similar average statistics for hitting, baserunning, and defense in their age 27-29 seasons. The list includes Ricky Henderson, Ichiro, Kenny Lofton, Tim Raines, Andy Van Slyke, Devon White, Derek Bell, Aaron Rowland, Steve Finley, and Marquis Grissom.

Fangraphs then took each of those players and looked at what they did in their age 30-36 seasons. Ellsbury will be 36 at the end of his 7-year deal. Important point noted by FG:

…here’s how these players did from ages 30 to 36, though not all of them stayed in baseball for the full seven years, so in their case its ages 30 to the end of their careers.

These are straight averages, not weighted by plate appearances, so Bell counts just as much in these calculations as Henderson does, and we’re not biasing these numbers up by giving more credit to the guys who kept playing.

The conclusion (again read the full article for the actual numbers):

Defense absolutely does peak early and should be expected to decline fairly substantially for any player heading into his 30s. However, history shows that players who are athletic enough to be valuable baserunners and defenders in their twenties are usually good enough athletes to maintain almost all of their offensive value as they get older.

…This player type has historically aged pretty well, and it’s simply not true that they become useless as soon as their speed goes…

In terms of WAR, Fangraphs arrived at a similar projection as we did:

Depending on how many plate appearances per season you’d project for him, an average decline according to what these 11 comparable players did would leave him as roughly a +3 WAR player for the next seven years. Ellsbury shouldn’t be expected to be a star for the duration of his next contract, but a sustained +3 WAR performance is nothing to sneeze at…If you put more credence on the fact that his recent performance is right line with what Henderson, Lofton, and Ichiro did in those same years, it’s not that hard to talk yourself into +25 WAR, which would equal about $150 million.