Jayson Werth and Why Age Matters

By now, it’s pretty well known that Jayson Werth underwent shoulder surgery and is expected to miss 2-3 months. If this news is shockingly unfamiliar to you, then I apologize for bringing this shred of misery into your life.

The injury, originally suffered last August, sheds some light onto a surprising lack of power from last season’s right fielder. Werth hit 16 home runs on the season, a career-low for any year where he’s played at least ¾ of the season, and only four of those homers came in the second half. An August injury doesn’t necessarily explain the two home runs he hit during a 52-game stretch from May through June, but at least it’s something.

If Werth returns to full health — a big if considering he’ll be playing 2015 at 36-years old — what can the Nationals expect from their new left fielder? More specifically, what does history tell us about aging outfielders and production? Our own Ricky Keeler argued that the Werth signing was a win for the Nationals. I couldn’t agree more.

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This article looks at expected value over the next three years of his contract. If history tells us anything, it’s that aging is not kind. Since the beginning of the 20^th century, there have been 204 individuals that have played at least 50% of their games in the outfield, totaling a combined 652 seasons, and the average player accumulated around 3.18 bWAR (bWAR is Baseball-Reference’s version of the WAR system. For a detailed explanation of the various systems such as from Fangraphs and Baseball Prospectus, look here) . That rather paltry number is inflated by the 51.3 bWAR Barry Bonds earned in seven steroid-fueled seasons along with Hall of Famers such as Babe Ruth, Ted Williams, and Willie Mays, so using the median instead we have 1.2 bWAR.

Not too promising.

Breaking that set down further by only using the ages 36-38 (the years we’re interested in with Werth) doesn’t help our cause either. Under those circumstances, the median value for bWAR drops to 0.5 with a season at the plate looking like .270/.326/.359 with four home runs in 315 at-bats.

But, I think to myself, Werth is a former All-Star who’s accumulated 31.1 bWAR in his career. He’s no slouch. There has to be a difference between exceptionally productive players who enter their late 30s. Taking that into consideration, I removed all the players from the previous list that never reached 30+ career bWAR, which also worked quite well in removing most of the early 20^th century players as well. Would it be fair to compare their numbers when they didn’t have access to things such as modern modes of travel, modern medical procedures, or ready access to nutritionists, supplements, etc?

Under these circumstances, the list is narrowed down to 82 players with a combined 331 seasons after reaching 36. The average career was worth 6.03 bWAR with the median coming in at 3.1. The good news is that the median value for seasons played was four, so at least the odds are good Werth will finish out his remaining three years on his contract. Unfortunately, in this model, the average season comes in around 1.5 bWAR.

You know, a borderline starter.

Before the panic sets in, recall that this spans the remainder of a player’s career. Usually those last one or two are fairly atrocious, so maybe Werth will be a run producing machine the next few seasons like he was in 2014. Specifically for the ages of 36-38, the median offensive values break down to .278/.349/.398 with eight home runs.

What about power hitters, though? Power hitters, or at least those with the ability to hit 20 or more home runs probably age a little differently, right? If we look at the age 36-38 seasons for players with 150 or more home runs by the age of 35 the numbers actually look slightly worse. The median value for bWAR sits at 1 and the median offensive season is .272/.337/.426 with 13 home runs in 117 games played. In all cases, the average season looks slightly better, worth about ½ win more, but not enough to write home about.

I could continue to break this data into subsets, looking to find a silver lining in this cloud. If there’s a bright side it’s that production follows a linear relationship to age. The average season for power hitters produces 2.14 bWAR at 36, drops to 1.5 at 37, and falls below 1 at 38, the final year of Werth’s contract.

Just for giggles, I made one more attempt to make Werth’s declining years more palatable. I cross- referenced the outfielders against all outfielders who had produced multiple seasons of bWAR of at least 4 prior to turning 36. Ugh. Again, the range of offense sits around .282/.349/.403 with eight home runs in 114 games played. The median value for bWAR comes in at 1.35.

Let’s just hope Werth ages like Zack Wheat who produced 12.6 bWAR through the age of 38.

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If we look at some comps, based on the similarity scores at Baseball-Reference.com, perhaps we can make a more educated guess. Using the similarity scores by age, Werth’s top three comps are Sid Gordon, Brian Jordan, and Carl Everett. Gordon played just two more seasons after turning 36, earned just under 3 bWAR, and retired at 37 as the ninth oldest player in baseball. Jordan was barely above replacement level over the course of four seasons, and Everett never played a game past the age of 35.

This makes me sad.

Well, if we jump all the way down to seventh in similarity score we find Matt Williams’ buddy Kirk Gibson. He had a decent career once turning 36. He was well past his heroic limping around the bases and questionable MVP season of ’88, but he earned around 3.5 bWAR in three seasons with Detroit.

Here is something worth being cheerful about: Fangraphs’ Steamer projects Werth to hit .285/.374/.454 with 17 home runs next year. Compared to the list I was looking over, that’s like the second coming of Tris Speaker. Offensively, he’s projected to do more of the same with another season of fairly atrocious defense. Steamer doesn’t know that Werth will play left and will likely morph into Jason Bay, but I don’t know that he won’t be better in left than he was in right.

Werth’s shoulder injury should terrify GM Mike Rizzo and the Nationals. Based on 114 years of aging men jogging after a baseball, Werth is destined for some rough years even under the best of circumstances. Will the shoulder heal properly? Even if he does, we’re likely past the point where Werth is a 20+ home run threat. I could be wrong, though. More than a century’s worth of data is probably too small of a sample size.

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