Short-Stop Analytics #10: Adrian Beltre: The Ageless Player

by: Jeff Adams – November 30th, 2018

The Hall of Fame ballot is one of the most contentious topics among baseball fans. Every fall, we begin anew the cycle of arguments about the players currently on the ballot and the players who announced their retirement at the end of the season. For every player that retires, there is a flurry of articles and tweets composed on what makes up a Hall of Fame career and whether that player deserves to be in the conversation. Sometimes, there is a general consensus on whether a player should get in, but there has never been a unanimous electee. This implies that there is always something to nitpick about any player up for election. Whether its alleged steroid use or an end-of-career dip in production, the BBWAA (and quick Twitter fingers) can find a flaw in just about anyone.

However, this year we’ve encountered someone quite different. Since his retirement announcement last week, one thing has been clear: Adrian Beltre is a Hall of Famer. I have yet to see one article or interview disputing that fact. Instead, there has been a tremendous outpouring of delightful anecdotes (like this thread) and lists of his statistical achievements. As a personal favorite player of mine, I would contend that Beltre has been one of the most complete players, let alone third basemen, to ever play the game. His offensive ability netted him 4 Silver Sluggers in a game crowded with great players at the hot corner. By all accounts, his glove was one of the few 80-grade tools to come through the game in recent history and that is shown by his 10th highest defensive WAR ever recorded at 29.3 wins. By bWAR, he is the 26th most valuable position player at 95.7 wins, flanked by Cal Ripken Jr. and Roberto Clemente.

There are a lot of ways to show how good of a player Adrian Beltre was, but there has been a lot written about that already from other outlets. Today, I wanted to take a slightly different approach and look at what I believe is the most impressive aspect of Adrian Beltre’s career: his ability to never hit an offensive peak. When Beltre came up as a 19 year old, he had mediocre stats and projected to be more of a glove-first infielder slashing .215/.278/.369. By no means was he anything close to what we just saw from Juan Soto. However, over the years, he progressed steadily and had an clear upward trend in his offensive production.

I fit a model to the data based on the method first described by Max Marchi and Jim Albert in Analyzing Baseball Data with R. This model assumes a player’s peak batting performance to occur at age 30. The quadratic nature of the model allows for greater ability to gauge when a player hits their peak. A typical linear model would be unable to show variation across a player’s career. The graph below plots Beltre’s offensive production (by wOBA) against his age.

Overall, Beltre’s career offensive production saw little to no decline at any point. Adrian’s Dodgers tenure saw the most volatility of his career with his wOBA skyrocketing to .421 in 2004. It is obvious that that season was an offensive outlier for him as it outstripped his next best season by 31 points. Even considering 2004, it is clear that Beltre was tremendously consistent at the plate. In fact, he did not reach his peak (according to my model) until the age of 36.

The general wisdom is baseball is that most players peak between the ages of 27 and 30. After that point, a player’s body traditionally begins to work against them. A typical aging curve has a normal parabolic arc with pretty similar amounts of the curve on either side of the peak. Beltre, on the other hand, has an extremely flat curve with 8 years consistent years around his peak.  As a good example of a normal aging curve, the graph below plots Babe Ruth’s wOBA against his age.

Ruth’s age curve is almost too perfect an example. He peaks at 30 and doesn’t spend much of his time around that peak. He declines just as quickly as he improved. Of course, it is worth noting that I am only seeking to compare the age curves here. Ruth is (one of) the greatest hitter(s) of all-time and only had three seasons with a wOBA lower than Adrian’s 2004 season.

How unique is he?

To really look at how impressive Beltre’s late peak is, we need to find a way to compare his curve with players that are most similar to him. From a dataset that includes every batter in MLB history with at least 2000 career at-bats, I calculated similarity scores for each player. The similarity score was originally developed by Bill James as a way to compare non-HOFers to HOFers. These scores are calculated by adding and subtracting points from 1000 for differences in various career statistics. Two players are more alike the closer the similarity score is to 1000.

After calculating the similarity scores, I fit the age model to each of the top 8 most similar players to Beltre. In order to show a player’s performance relative to the league, I fit the same model to the league-wide wOBA measurement in a given year. Of the nine batters included, only two are not currently in the Hall of Fame. Both of those players (Beltre and Beltran) have not been retired long enough to make the ballot. Every other batter has a noticeable after peak dip with only Chipper Jones having any sort of uptick near the end of his career. No other player has a peak age anywhere near Beltre’s (shown by the dotted line). The lack of any extreme curvature further emphasizes how consistent he was.


Adrian Beltre was a special player. This exploration of his aging curve only focused on a single facet of a phenomenal career. There have been players with greater offensive numbers, but not many that demonstrated his level of play across an entire career. In some ways, it was actually his ability to consistently improve as a batter and maintain a solid glove that has seated him so clearly in the Hall of Fame discussion. From his time in L.A. to solidifying himself as an Ranger forever, we have been privileged to watch a truly ageless player and I, for one, can’t wait to see him enshrined in Cooperstown.

Data courtesy of Baseball Reference and the Lahman Database

Photo courtesy of AXS

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