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The aging curve for starting pitchers in baseball probably looks like what you would expect. Starters come into the league with flaming velocity and a high walk rate, their stats improve as they age until they peak, and then we see a steady statistical decline from that peak until the end of their career. What age does that peak come, though?
As you can see from the graph above from Fangraphs, the peak age for starting pitchers comes at 26. It’s after age 26 that pitcher velocity and strikeout rates begin to really decline and walk rates and FIP begin to steadily rise. It’s at age 26 that we can expect top performance from starting pitchers, which is good for Twins fans as their ace heading into the 2020 season, José Berríos, will turn 26 in May.
Until this point in his career, Berríos has improved each season and followed the general aging curve shown in the graph above. His velocity (slightly) and walk rate (greatly) have declined while his strikeout rate and FIP have improved in each season. If Berríos continues to follow the aging curve that he has followed throughout his career, we could be looking at a peak Berríos season in 2020.
Another thing that I looked at while I was studying the starting pitcher aging curve was to look at other recent examples of starting pitchers and how their age 26 season compared to the rest of the career. For this exercise I looked at starting pitchers who were free agents this season as we have them all fresh in our minds.
In the graph above I compiled statistics from Madison Bumgarner, Stephen Strasburg and Dallas Keuchel before, during and after their age-26 season to see how they compared. I highlighted in green when their age-26 stats represented a “peak” meaning they improved upon their career stats up until their age-26 season as well as showed a career decline in that statistic following their age-26 season. As you can see, most of these players posted career bests in their age-26 season, supporting our aging curve discussed above to be an accurate depiction of a pitcher’s career.
So what does this mean for José Berríos? To this point in his career, José Berríos has posted a 4.21 ERA, 4.10 FIP, 8.8 K/9 and 2.3 BB/9. Expecting Berríos to improve on those career statistics in 2020 seems like a certainty. But just how much will he improve? If he can continue on his career trajectory and follow the starting pitcher aging curve, I think we should all be really excited about what next season could bring for the Puerto Rican right-hander. He could really be the ace that we were unable to acquire in free agency.
What do you think we can expect from José Berríos heading into 2020? Leave a comment below to start the conversation.
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