Tomorrow we will be posting our updated Trade Value Index, in which we rank the top 45 players in the organization based on overall value to the franchise. Two of the most important criteria for determining overall value is a player’s age and the number of years remaining until that player is eligible for free agency.

In this post we are going to show you how we calculate this value. We will also take a look at what the optimum age is for promoting a player to the Major Leagues so that the Rays can maximize a player’s value. And finally we will show you how all the Rays players rank based on age-value (AV).

We know that a player’s peak age is about 27. This is great if you are able to build a team with 25 27-year olds and then get 25 new 27-year olds next year. But players usually stay with a team for more than a single season.

So what is the optimum range of ages to have a player on your team? Let’s say you can have a player for two seasons. On average, is it more valuable to have that player for ages 26-27 or ages 27-28? To know this we need to know how valuable the age-26 and age-28 seasons are compared to each other and relative to the age-27 season.

Luckily, the guys at The Book have already done that part of the work for us. Using several key stats for hitters, they calculated linear weights to each age from 21 through 39. If we graph these values we get an idea of how players age…

As we can see, the curve peaks at age 27 (linear weight=0.999) and a player is a little bit better at age 26 (0.996) than at age 28 (0.978). So in our original hypothetical situation, if a team can only have a player for two seasons, they would usually be better off with the ages 26-27 than the ages 27-28.

Now let’s extrapolate this and determine AVs over all possible combinations of age and number of years a player is with the team…

In the first column we see the original linear weights from The Book. To calculate the AVs for the other columns we simply added the values for each age-season a player would be with the team. For example, if a player debuted at age 21 and is with the team for six seasons, his AV is calculated by adding the values in column 1 for ages 21 through 26.

So at what age should a player make his big league debut if the team is to maximize the player’s AV*? If we assume that the player will be with the team for six seasons and leave once they are eligible for free agency, then a team can maximize a player’s production by having the player debut at age 24. This would cover a player’s ages 24-29 seasons.

Now let’s look at the AVs for Rays on the 40-man roster and a few of the top prospects. Notes on this table can be found below…

Notes on the table…

  • The original linear weights were for hitters. It has been argued that the peak season for pitchers is also age 27. However, we do not have linear weights for other ages. So for the sake of this analysis we are assuming that the curve seen above is the same for pitchers.
  • We used ages for the 2011 season and control refers to the number of years remaining until free agency starting with 2011. Basically, we are looking at value beyond this season. Therefore, players that will be free agents this winter have AVs of zero.

As we can see, Jeremy Hellickson, Desmond Jennings and Jake McGee will all be in their age-24 season next year. If they make their big league debuts (as expected), the Rays will be maximizing their values. Evan Longoria’s AV falls below these three because his 6 remaining seasons cover ages 25-30, which is slightly less valuable than the ages 24-29 that the three prospects will likely spend with the Rays.

At the other end of the spectrum, several key members of the roster have low AVs. This is because these players are nearing free agency (e.g. Matt Garza, BJ Upton). So while these players will be in or near their peak season (age-27), much of their value has already been used.

Obviously there are a lot of other factors that go into determining a player’s value. But for a team like the Rays, they need to maximize that value at every turn. Most of the Rays talent will come from within the organization, and most of those players will leave by the time they hit free agency. It is the nature of the beast. And if the Rays are going to tame the beast, they need to maximize AVs.

(a special hat tip to Sky Kalkman of Beyond the Boxscore who pointed me to the linear weights data)

*A player is eligible for free agency once they hit 6 years of service time. However, depending on when a player makes his debut, it is possible for a team to get (nearly) 7 seasons from a player before they become eligible.



  1. Jason Hanselman says:

    Cork, this is really impressive, kudos on the hard work. I'm psyched that we're going to have Matty Joyce for his age 35-41 seasons by the time he get's promoted. By my math, that's an AV of infinite.

  2. VC says:

    Loikong at the final table i see that all players with 6 years of control are greater than all players with 5 which in turn are all greater than the 4s. I think most people knew that already.

    • Cork Gaines says:

      Yes, all other things being equal a player with 6 years is worth more than one with 4 or 5. What I am attempting to do is place a number on that. A number that is part of a bigger formula (TVI) that does incorporate other factors.

      But even just using this data there is stuff we can see that may not be so obvious to most fans. For example, players like Joyce and Jaso and Perez are already moving through their peak years. So if and when these guys are promoted this tells us that their max shelflife with the Rays is probably 6 seasons and in all likelihood will be less than that.

      Also, these numbers show that the Rays are not being too patient with prospects like Jennings and Hellickson as next year would be the best time to start their big league careers.


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