Michael Bourn is a pretty terrific defensive center fielder. Last year, he was the best defensive outfielder in baseball by UZR (after you account for the positional differences), grading out as 25 runs above an average defensive player, and it wasn’t a one year aberration, as no player has a higher FLD+POS rating over the last four years either. With over 6,500 innings big league innings, we’re not dealing with problematic small samples either. Bourn has been a tremendous defensive asset this far in his career.
However, teams are no longer as willing to pay for past performance as they used to be, as front offices are now populated with people who are more interested in projecting a player’s future than they are with paying for an established track record. So, while Bourn’s defensive performances are notable, they’re only worth paying for to the extent that they inform our understanding about what they mean for his defensive value in the future. Now 30-years-old, Bourn’s getting further and further from his peak, and defensive skills seem to plateau earlier than offensive skills, so there’s some legitimate questions about just how much of his defensive value he will retain in future years.
To try and shed a light on that question, we can identify players who were valuable defensive outfielders in their twenties, and then see how much of that value carried over to their thirties. If you’re Michael Bourn, or Michael Bourn’s agent, you might want to stop reading now, because the answer probably isn’t something you’re going to want to hear.
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