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Projecting the Tampa Bay Rays: Comparing Steamer and ZiPS

Where do they agree? Where are the arguments?

Slugger? Or SLUGGER?!?!?
Slugger? Or SLUGGER?!?!?
Ron Chenoy-USA TODAY Sports

Today was a big day for Rays fans. It's not the start of spring training (although the equipment truck should have reached Port Charlotte by now), but it's the the next best thing: release day for Dan Szymborski's ZiPS projections for the Rays.

PECOTA has yet to drop, but Steamer has been available since early in the off-season, and that now means that we have two high-quality projection systems to compare and think about.

Why Projections?

Computer projection systems aren't magic, and we shouldn't treat them as such, but they're an important tool for being an informed fan.

Think about your expectations for a player. What are they based on? You probably think about what a player's done over the past several seasons, how old they are, whether or not they were injured, how athletic they seem, how smooth is there swing, etc.

Computer projection systems only know the parts of a player's game that are evident in the box score, so there are cases in which you can do better with the additional information that you, a human, might know. But the projection system does a much more thorough job considering the information that it is privy to, and that makes them an invaluable starting point.

Think of them as taking the prior statistics and age, mixing them with a lot of historical knowledge of baseball, and then spitting out an average expectation.

All of those other things that you the human know, along with a bunch of luck (injury and otherwise), will make the players actual season either lower or higher, but you need a solid foundation on which to apply your specialist knowledge.

The 2016 Rays

Both Steamer and ZiPS are good systems, but because they look at slightly different stats in slightly different ways, they output a slightly different set of numbers. If you want the best projections, look at both and take the aggregate. But it's more fun to keep the components around while you do that and think about the differences.

wOBA is a statistic that weights each offensive outcome relative to how much they help a team score runs. It is set tot he same scale as OBP.

Here they are the 2016 projections in colorful form.


And here they are again, but for those of you who like sortable tables (click on the tops of the columns to sort by that value).

Player Steamer Proj. wOBA ZiPS Proj. wOBA Average Difference
Corey Dickerson 0.319 0.333 0.326 0.014
Steve Pearce 0.322 0.324 0.323 0.002
Evan Longoria 0.325 0.321 0.323 -0.004
Steven Souza 0.318 0.327 0.323 0.009
Logan Forsythe 0.314 0.321 0.318 0.007
Brandon Guyer 0.314 0.317 0.316 0.003
Kevin Kiermaier 0.307 0.320 0.314 0.013
Brad Miller 0.312 0.315 0.314 0.003
Logan Morrison 0.314 0.310 0.312 -0.004
Desmond Jennings 0.306 0.317 0.312 0.011
James Loney 0.306 0.299 0.303 -0.007
Nick Franklin 0.300 0.298 0.299 -0.002
Richie Shaffer 0.294 0.290 0.292 -0.004
Curt Casali 0.289 0.291 0.290 0.002
Hank Conger 0.287 0.291 0.289 0.004
Mikie Mahtook 0.285 0.291 0.288 0.006
Tim Beckham 0.270 0.282 0.276 0.012
Luke Maile 0.261 0.264 0.263 0.003
Rene Rivera 0.263 0.257 0.260 -0.006

Here are a few observations:

  • The aggregate projections think that the Rays best hitter this season will be Corey Dickerson, with a .326 wOBA overall. That seems reasonable, as in 925 career plate appearances, Dickerson has put up a much-higher .377 wOBA. Of course that came in Colorado, an extreme hitters' park, and he'll be moving to a pretty extreme pitchers' park, so that's where the large drop-off comes from. The interesting thing about Dickerson's projection is that he has the largest difference between ZiPS and Steamer of any Rays player. I'd wager that has something to do with how they're treating the stadium transition.

  • Next comes three players tied with the same overall projections. Steamer and ZiPS agree very much on Steve Pearce, and are pretty close on Evan Longoria as well. There's more discrepancy on Steven Souza, with Steamer becoming a little discouraged by Souza's 2015 (relative) struggles, and projecting him for more of the same in 2016. ZiPS thinks there are better years ahead.
  • It's odd to look at the Rays and see Longoria as arguably the fourth best hitter. There are two ways to react to this: 1) That's really disappointing for Longoria. 2) Wow! The Rays have three other guys as good as Longoria! Woot!
  • There are a few other big swings in projections between the two systems, and two of them also come in the Rays outfield. ZiPS rates both Kevin Kiermaier and Desmond Jennings significantly higher than Steamer overall, and it's a difference that matters. In the world of ZiPS, both of those guys are clear everyday players. For Steamer, they look more like guys you want to platoon. Which system is more right about Kiermaier will have a lot of bearing on the Rays' fortunes over the next several years, and which system other teams believe is right about Jennings will have to do with what they're currently offering the Rays for him in trades.
  • I think that ZiPS generally assigns a bit more weight both to extreme performance and to recent performance than does Steamer (I may be totally wrong on this), and it's a little bit higher on Logan Forsythe, which offers some confirmation bias to that theory. Both projections see Frosty as a good guy to have around, but maybe not his Team MVP caliber from last season.
  • ZiPS is either similar to or more bullish than Steamer on all of the possible starters, except for one. James Loney did not have a good season in 2015, and while Steamer thinks he can bounce back to the point where he'll be useful against right-handed pitching, ZiPS thinks Loney's days as a starter or even a useful platoon are mostly over.
  • There's a wide discrepancy between what Steamer and ZiPS think of Tim Beckham, but neither of them think he'll be very good.
Today we looked at the overall projections. Tomorrow we'll go more in depth and look at how these projections combine with handedness splits, and start building the possible Rays lineups.