Predicting How Pujols Might Age

Obviously, no one knows how Albert Pujols will age. But if we want to make an estimate, how can we do so?

Albert Pujols is an exceptional talent and a great player to root for. Given my choice, Albert will be batting cleanup for Cardinals and contending for a triple crown when I take my grandchildren to a game in 2024. However, given that he will be 44 by then, that is not likely. Much to my dismay, he will eventually prove to be mortal and show the effects of age.

One way to estimate how quickly Pujols will succumb to the effects of time is to look at other similar players. The difficulty here is that Pujols is a unique talent—few players are similar to him. But if we want to use hard data, that is the best we can do. If nothing else, by combining players, we can learn something from the shape of the data.

What follows are the results of a small, quick study I did on the aging of players similar to Albert Pujols. The WAR numbers are from Fangraphs. I am aware that this is not an incredibly statistically sophisticated study, but it is better than picking a player out of the blue who did not age well and simply using them as an example. 

Study 1

The first set of players I used was the Baseball Reference.com list of players most similar to Albert Pujols at age 30. This generated the following list:

Jimmie Fox, Frank Robinson, Ken Griffey, Lou Gehrig, Hank Aaron, Mickey Mantle, Mel Ott, Juan Gonzalez, and Manny Ramirez.

This list is a bit odd, as it seems very heavy on OF. On the other hand, it includes a list of highly talented superstars who could rake.

For the study, I decided to exclude Juan Gonzalez, as he seems totally out of place on this list. For example, the other players averaged a 7.6 WAR from age 27-30, while he averages a 3.3. Pujols averaged an 8.43.

One issue with the list is Jimmie Foxx left for the war at age 35 and missed most of two years. However, it is unclear how negatively this impacted his performance—in his final 100 games before leaving he only managed a WAR of 0.6.

I next tried to set an established value level. To do so, I simply averaged the WAR of the group of  players’ age 27-30 seasons. I went up to age 30, as that is the current age of Pujols. Using 4 years was admittedly arbitrary, but players tend to be stable throughout that time of their career. Using three years of data--ages 28-30--does not change the data much—there is a difference of less than 0.2 of WAR.  

For each subsequent age, up to 38, I computed the group’s total WAR for that age. Then I divided it by the group’s established level of production. This told me how much of their established value level they retained at that age.

For example, the group of players as a group averaged a WAR of 68.375 from age 27-30. At age 31 the group produced a WAR of 59.6. This amount was 87% of their established level of production.  

Then, to derive an estimate of what value Pujols might have at this age, I multiplied the percent of their established value the other players retained by Pujols’ established value. For example, if they retained 87% of their value, I project he will retain 87% of his established value, too.

The results are as follows.

Study 2

I ran the same study again, but this time I used Baseball Prospectus.com’s most recent list of similar players. This list was generated before the 2010 season. It does list many more first basemen. The list is as follows:

Frank Thomas, Jeff Bagwell, Jason Giambi, Eddie Murray, Lou Gehrig, Rogers Hornsby, Travis Hafner, Todd Helton, Jack Clark, and Fred McGriff

From this list, I excluded Travis Hafner for a variety of reasons. Mainly, at 33 years old, he does not provide much data on aging. I also considered eliminating Jack Clark. I left him in, but I am happy to provide results excluding him if anyone wishes.

The players had an average WAR of 6.5 during their age 27-30 seasons.

The results are as follows:  

Discussion of results

The studies are far from flawless, but they do yield a few interesting results. Study 2 suggests a much more gradual aging curve for the next five years of Pujol’s career. Overall, however, they both predict a steep drop from age 36 to 38. At these ages many players in the studies often lost most of their productivity or left the game altogether. In short, despite these being lists of elite players, most rapidly lost their value after the age of 35.

In addition, if one looks at the data, there is no clear way to determine who will hold their value.  

Based on these results, a five-year contract, even at a higher annual value, would probably be optimal. Of course, it is also highly unlikely.

The best case scenario from the players studied was Hank Aaron. In his age 36-38 seasons he produced WARs of 5.9, 7.6, and 5.1. If Pujols could retain a similar value, he would be worth a high annual salary even in an 8-year contract. However, Aaron was an extreme outlier in the study—no one else was even close. Four of the players studied had little or no value after age 35, and Todd Helton seems likely to join them.