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Predicting how Yasmani Grandal will age

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Catcher aging curve and comparison to other elite backstops will hopefully provide answers.

MLB: NL Wild Card-Milwaukee Brewers at Washington Nationals Geoff Burke-USA TODAY Sports

One day after the World Series, Yasmani Grandal’s representatives announced that he would decline his $16 mil mutual option and go into free agency.

The signing of Yasmani Grandal was one of the best deals of the 2018-19 offseason. The catcher exceeded the value of his contract in 2019 by slashing .246/.380/.468, blasting a career high 28 home runs, walking over 100 times, and posting 5.2 fWAR. He carried Milwaukee offensively during the most recent campaign, and without his contributions, it is unlikely the Brewers make the playoffs. The only other active catcher that even compares right now in MLB is J.T. Realmuto.

Grandal will hit the open market as the #1 free agent catcher available. With a void at starting catcher, Milwaukee has to seriously consider re-signing the All-Star backstop. But with what common senses suggests will be an inevitable and potentially significant decline in the not-to-distant future, why spend major dollars on locking up the catcher for a longer term as he enters his age-31 season? It is a legitimate question, and one that David Stearns is probably weighing heavily.

Yet do backstops decline any more than other position players do? It would seem reasonable to think so. The phrase “donning the tools of ignorance” is not for nothing as catchers take a beating behind the plate. Data should support this reasonable, and logical thought process.

According to Dave Cameron (now with the San Diego Padres research department), the decline of MLB catchers in their early 30s is NOT supported by the data. In a 2017 article for Fangraphs, Cameron wrote:

“There simply isn’t this huge early-30s drop-off that is widely accepted as a fact of life for catchers. The existence of a huge cliff at which productive catchers simply turn into useless backups isn’t supported by the data. Like players at all other positions, catcher aging is a mostly linear downwards trend, and there just aren’t certain ages at which player performance gets exponentially worse.”

Cameron illustrated this with a graph he pulled from Jeff Zimmerman of Fangraphs:

Jeff Zimmerman’s Catcher Aging Curve

Again, Yasmani Grandal will be entering his age 31 season. He just posted his second-best fWAR season to date. He has not posted an fWAR below 4.1 since 2015. Grandal has been consistently terrific through is peak years and is the epitome of a productive catcher. He is now approaching the decline phase of his career, but just like Dave Cameron said, he is not likely to fall off the cliff, especially since he has been relatively healthy throughout his career.

Based on the graph above, Grandal should have begun his steady decline around age 28-29, yet he performed as well as ever at age 30. Cameron goes on to points out that a fall off should be about -0.5 WAR per season. That is obviously not a hard and fast rule, and productive players like Grandal have further to fall before they are no longer contributing. As the graph above illustrates, catchers normally decline like every other positional player up to the age of 32. Interestingly at that point, catchers actually age better than other position types, which likely makes them a better value than other position types to sign into their late careers.

Something else to ponder is the fact that only five active catchers have posted better fWAR since 2010 than Mr. Grandal — Buster Posey, Yadier Molina, Jonathan Lucroy, Russell Martin, and Brian McCann. Couple that with the number of games he has played versus these other catchers in that same period, and his numbers are even more remarkable.

So let’s go back to the idea of catcher aging. Each of the five catchers mentioned have experienced declines in their offensive and defensive performance as they aged. All are older than Grandal, and comparing him to these five catchers might offer insight into how he might age.

Buster Posey

Over the past decade, no other catcher has been as good as Buster Posey. He’s posted 53.0 fWAR over the last 10 years, but at 32 years old, his best work is behind him. Posey is an example of a catcher who has fallen off, if not a cliff then, a steeply inclined hill. He posted 6.7 fWAR in 2016 and followed that up with 4.7 fWAR in 2017, but he hasn’t approached that level of production since. He dropped to 2.3 fWAR in 2018 before falling to 1.9 last season.

Once the best dual threats at the position, the Pose has diminished significantly with the bat, slashing a meager .257/.320/.368 in 2019. He still does bring value to the Giants defensively, just not to the same degree. He was once one of the best defensive catchers in the sport. In 2016 he posted the best Defensive rating of his career at 39.5 adjusted runs above average. In 2019, he posted a still-strong Def rating of 18.3.

Posey has had at least two concussions in his career, and he’s also undergone hip surgery. Could those head injuries have impacted his decline? There is no other position in baseball more vulnerable to head injuries than catcher. With Posey’s rather steep decline beginning after his age 29 season, it is reasonable to surmise that he was affected by injury, especially to the head.

Jonathan Lucroy

Jonathan Lucroy is arguably the best catcher to ever wear a Brewers’ uniform. But once traded from Milwaukee, his star not only faded, it has dissolved into the darkness.

Sicne the beginning of 2010, Lucroy has posted 37.0 fWAR. From 2011 to 2014, he rivaled Buster Posey and Yadier Molina for best catcher in the sport. His framing numbers were incredible (+41.5 runs in 2011 and +34.0 runs in 2013). He was strong at blocking, throwing out would-be base stealers, and handling a pitching staff. On top of that, he was an excellent hitter posting an .855 OPS in 2016 for his finest season at the plate.

The Brewers cashed in at the right time and sent Lucroy along with Jeremy Jeffress to Texas in a trade that brought back Lewis Brinson, Luis Ortiz, and Ryan Cordell. It seemed that once he left Milwaukee, everything fell apart for the former All-Star catcher. He could no longer hit (wRC+ of 80 in 2017, 71 in 2018, and 77 in 2019). He could no longer steal strikes like he once did. In fact 2014 was the last season the one-time poster boy of pitch framing posted strong numbers (+18.2 runs).

Grandal is now the poster child of pitch framing. Could there be a similar drop off to Lucroy? While no one admits to this publicly, Luc is probably the victim of concussions. We all remember the vicious hit that he took from Jake Marisnick.

Remember too that Lucroy suffered a concussion that ended his season in 2015. There is no telling what the impact of that injury and subsequent shots to the head had on him. What we do know is that Jonathan Lucroy fell of the proverbial cliff in terms of his offensive and defensive performance.

Yadier Molina

A lot of people think of Yadier Molina as having a slow decline, but in fact, Molina dropped from an elite level player to a good player rather quickly. Each year from 2008-2013, Molina posted between 4.5 fWAR to 7.8 fWAR. He was one of the best defenders at the position while posting a few really nice seasons at the plate. But in 2014 Molina’s production dropped to 3.4 fWAR, and he would post between 2.3-3.5 fWAR in the subsequent seasons until 2018.

Taking age into account, Molina’s last elite year (and every season previous was elite) was his age-31 season. He fell from 7.8 fWAR to 3.4 fWAR between 2013 and 2014 but would continue to produce at similar levels until 2019, his age 37 season (1.2 fWAR). Molina has aged well, continuing to be a worthwhile member of the lineup even if he’s no longer a star. He has remained pretty healthy for his entire career, which is something to consider as the Brewers look at Grandal moving forward and his relative good health to this point.

Russell Martin

Russell Martin was a very good catcher for a very long time, posting 3.1 fWAR to 7.9 fWAR (2008) from 2007-2016. Unlike Molina, Martin has become more of a part-time player later in his career. With that he still contributes positively (between 1.2 fWAR and 2.0 fWAR over the past three seasons), but his irregular playing time prevents him from accumulating WAR like a full-timer. Martin was All-Star level as late as his age-33 season. Martin is one of those catchers who have enjoyed relative health throughout his career as well.

Brian McCann

Brian McCann produced early in his career. At the age of 24, he produced a 8.6 fWAR. Over the next three seasons, he would produce between 6.3 fWAR and 6.9 fWAR. He would fall off a bit after that. At the age of 28, McCann had an All-Star level season (4.2 fWAR). He would not be above 4.0 fWAR ever again.

McCann still contributed as a solid starter. From the age of 29 to 32, he played most of the games at catcher for his team. His decline was obvious though. In 2019 McCann was 34 years old, and he posted a solid 8.3 Def rating. He also posted an 89 wRC+, which was slightly above-average for his position, but he is no longer a legitimate threat at the plate. Yet of the four catchers listed, McCann ranked highest in wRC+ for 2019.


By comparing Grandal to the five catchers that have achieved higher fWAR than him over the past decade, we can surmise how he might age. Martin and Molina posted elite level numbers at age 31 as they had up to that point. Each fell off significantly after that, although both continued to be good. Lucroy and Posey are no where near the players that they were, but head injuries may have been part of the reason for that. McCann contributed throughout his career well beyond his All-Star days.

Grandal will be 31 in 2020 and he has a long way to fall before his production is no longer useful. He has been pretty healthy, especially with regards to his head, so Russell Martin and Yadier Molina may be his best comparison points. If that is the case, Yaz should put up another All-Star to elite level season in 2020, but a fall off would occur in 2021. Grandal is still a very good player and is likely to be a good player over the next few seasons. With that in mind, how should David Stearns proceed?

Baseball statistics courtesy of Fangraphs