In a recent episode of the Effectively Wild podcast, a listener emailed co-hosts Ben Lindbergh and Jeff Sullivan a question about the modern evolution of constructing a bullpen. The latter’s response included the following remark about the volatility of relief pitcher performance, specifically from the end of one season to the beginning of the next:
I think it’s actually dangerous to invest in non-elite relievers before the season because you just don’t know how much of that [previous season’s production] is going to carry over and then it would make sense to add during the season when I think–I guess if I had to simplify, I think first-to-second half reliever performance is more reliable than season-to-season reliever performance when you’re talking about guys who aren’t the absolute cream of the crop.