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Projection Systems

One of the more common questions asked of me is in regards to projection systems. Which should people "trust", how they should be weighed, and is PECOTA worth paying for.  In reverse order, let me say that PECOTA is excellent. It's quite impressive and if you have a Baseball Prospectus subscription for the content already, then you really cannot go wrong using PECOTA. With that being said, paying simply to access the weighted means spreadsheet is hardly necessary to get an appropriate read on projections.

For instance, say you wanted to know what the systems are saying about Pat Burrell. Well, you could purchase a BP subscription and figure his wOBA the longhand way (1.75*OBP+SLG/3) and get .364 as your answer. Or, you could go to FanGraphs' player page for Burrell and have access to CHONE, ZiPS, and Marcels projections which say: .355, .369, and .377. Average those three and you get ... drum roll ... .367. Even if PECOTA is more accurate in this case, we're talking a fairy insignificant difference.

If you enjoy being a slave to information, you could always throw the PECOTA projection in as well and get a four system average, but it's not necessary if you don't already have access to PECOTA. As you'll see below, I've taken the means to gather the projections and average them out between the four systems and the three free systems.

Last PECOTA CHONE Marcel ZiPS 4S Avg Free Avg
Pena 0.368 0.382 0.383 0.388 0.38 0.384
Burrell 0.364 0.355 0.369 0.377 0.366 0.367
Longoria 0.36 0.36 0.366 0.365 0.363 0.364
Upton 0.355 0.372 0.358 0.367 0.363 0.366
Gross 0.354 0.336 0.335 0.337 0.341 0.336
Kapler 0.34 0.323 0.337 0.334 0.334 0.331
Aybar 0.332 0.336 0.334 0.317 0.333 0.329
Crawford 0.324 0.357 0.335 0.347 0.341 0.346
Iwamura 0.323 0.325 0.33 0.324 0.326 0.326
Ruggiano 0.319 0.333 0.312 0.326 0.323 0.324
Navarro 0.318 0.321 0.319 0.312 0.318 0.317
Zobrist 0.318 0.33 0.309 0.323 0.32 0.321
Joyce 0.312 0.318 0.354 0.329 0.328 0.334
Bartlett 0.296 0.318 0.315 0.315 0.311 0.316
Perez 0.295 0.312 0.341 0.288 0.309 0.314
Riggans 0.288 0.298 0.312 0.292 0.298 0.301

I'm sure you've noticed the numbers aren't entirely different - the average difference is like 0.001 points -- and it's obvious why; we only took one of the four parts out of the equation and PECOTA is pretty much in line with what the other systems are forecasting.

Another extremely important thing to note is that league averages for each of these systems are unique. If you go to FanGraphs and see that two projection systems peg a player for a .330 wOBA and then glance to the wRAA column, odds are the two numbers will vary. Perhaps not be by much, mind you, but some (Marcels especially) depress offense and others (Bill James, which, incidentally, is why I don't use them) inflate offensive output drastically.

Okay, that pretty much answers the questions, but let's go a bit further here. Each forecasting system has some drawbacks. Try and use these to get a ballpark feel for how a player is expected to perform, but keep in mind there's a good chance that said player will exceed or fall below the projected line. Again, this is mostly common sense stuff, but sometimes it needs to be stated. If Burrell has a wOBA of .350 someone will say "But PECOTA said..." and that's simply a misinterpretation what these projections are supposed to be used for.

As for pitching stats, you can easily do the same. I know RGlass has a PECOTA sheet with FIP numbers thrown in, perhaps he can share those.