March 26, 2011
Improved SS/SIM for 2011
We recently went to great lengths to develop the new version of SS/SIM, the Scoresheet simulation value metric here at Baseball Prospectus. As fellow Scoresheet owners, we realize that optimally these valuations would have been complete several weeks ago. Unfortunately, the original formulation of SS/SIM was not available to us this year, and our replacement took more time to develop than we had anticipated. We set out to create an all-new run-based value metric for Scoresheet team owners to use in player valuation. This time consuming effort was spearheaded by BP staffers with Scoresheet experience, and included research into the Scoresheet engine, talking with Jeff and Dave Barton, and consulting with Scoresheet experts for feedback.
Development of SS/SIM for both hitters and pitchers starts with the Scoresheet definition of replacement level, namely the awful Triple-A players that are used when you run out of playing time in the Scoresheet simulation. From there we have captured the most important aspects of the Scoresheet simulation and built them into the SS/SIM methodology to produce a single metric for Scoresheet owners. These adjustments seek to raise the effective replacement level and account for the differences between MLB and Scoresheet. [edit: BJM 2011-03-28]
The offensive formulation builds a value estimate from the replacement level based on expected offensive output. The offensive valuation is built from a positionally adjusted perspective that also emphasizes overall offensive output, supplemented with a defensive adjustment that accounts for each player's Scoresheet defensive eligibility and range rating, as well as a penalty for expected errors.
The results of this process are valuations that use a very low replacement level--note that Player(AAA) is remarkably low in value compared to the replacement level used for metrics designed for evaluating MLB players. SS/SIM as a hitter metric provides a complete depiction of a player's value in Scoresheet because it uses replacement value specific to Scoresheet and incorporates the latest research on Scoresheet defensive range value and appropriate valuation of errors to form a comprehensive view of the player.
The pitching for>mulation is a bit more complicated. Pitcher valuation is based around projected IP and ERA because the foundation for value in Scoresheet for pitchers is their ERA, and because pitchers in Scoresheet are basically limited to their real life playing time. Because we expect Scoresheet owners to alter pitcher usage based on ERA, each pitcher is projected to throw a certain percentage of his real life innings for the Scoresheet fantasy team. The projection for how many of his real life innings will be utilized is separated by starters and relievers based on the expectation that Scoresheet managers will maximize usage of their relief pitchers because they have lower ERAs, which is the converse of real life MLB usage. As a result of this usage pattern, the ratio of SP IP to RP IP is lower in Scoresheet than MLB, and our methodology reflects that difference as well. We also put a premium on pitchers whose ERA is better than league average to account for the importance of ERA and the multiplicative nature of actual run production in the simulation. This adjustment is proportional to the extent that a pitcher is better than replacement level, so it impacts premium starters the most, but it also increases the importance of very good relievers as well. Given the expectation for how many innings a pitcher would pitch for his Scoresheet team, we can derive his SS/SIM by comparing his forecast for runs allowed over that time to what the Pitcher(AAA) would allow.
The results of this process are valuations that use a low replacement level, and also incorporate several differences between Scoresheet and MLB. Primarily, the significance of ERA within the simulation is because of how expected runs are scored, as a product of expected runs allowed by pitchers and expected runs scored by hitters, more or less. This multiplicative effect is captured in SS/SIM through the premium placed on elite pitchers. Additionally, a pitcher's ERA is the primary driver in our adjusted usage patterns, which capture the difference in usage between SP and RP from Scoresheet and MLB. SS/SIM as a pitcher metric provides a complete depiction of a pitcher's value in Scoresheet because it incorporates all of these factors to form a comprehensive view of each pitcher.
We expect that as a run based metric, SS/SIM will have an approximate equivalency of 10 runs to 1 win. In practice, we hope that SS/SIM helps as a way to measure players of different positions against each other, and on a large scale, to help identify what value to expect from each player. On a more granular basis, because these are projected values, small differences in SS/SIM are probably worth prioritizing below other considerations, like team needs and draft context. Comparisons between pairs of players, especially when looking at draft picks after the middle of the draft, should largely be based on team composition to that point--whether you need 175 IP at 4.55 ERA or 65 IP at 3.60 ERA largely depends on who else you have on your roster.