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Old 01-30-2020, 03:15 PM
Jas09 is offline
Join Date: Jan 2007
Location: St. Louis, MO
Posts: 5,777
Originally Posted by Fotheringay-Phipps View Post
It's impossible to "isolate what the hitter is responsible for from the context surrounding him". Outside the context surrounding him, any hit other than a home run is worth zero, for example.
Well, I'm not sure I agree with that. Clearly a hit is worth some part of a run. The problem was that a player with 200 hits (but no HR) on a team where nobody else ever got on base was showing up as being worthless (no runs, no RBI) when clearly he isn't. So by using linear weights to determine what portion of a run a single is worth (and similarly a double, triple, SB, moving from first to third on a single, etc) you can at least begin to compare a good player on a bad team to a bad player on a good team.
It would seem obvious that the value of any stat is completely dependent on an assumption as to what the other members of the team are likely to do (or to have done). My question is essentially whether that assumed likelihood is based on league averages (or something along those lines) or reflects team averages (or similar).
It is based on "average teammates" basically. Over the entire history of baseball the linear weighted value of a hit is worth something (based on baserunner and out combinations at the time of the hit). You scale all of those weights and generate your "offensive value" metric. You can see some of the guts of that for wOBA here: The nut of it is: "For wOBA, we have the runs above average for walks (0.29), HBP (0.31), singles (0.44), doubles (0.74), triples (1.01), and home runs (1.39)"
Where it would matter is when you're trying to use the individual metrics to project wins for the future, versus assessing the past. So if you up your team's WAR by X on an individual level, does that translate to X additional wins for the team?
At a first-order level, yes, adding a 5 WAR player to replace your 3 WAR player should add 2 WAR to your team wins. I have no doubt that more sophisticated modeling and simulation software could plug that player into an existing lineup and generate some sort of mean/stdev prediction for additional runs generated. Then you have to convert runs to wins, which obviously depends a bit on things like bullpen strength, and possible even your manager's tactical competence.

Predicting baseball is hard...