Who Can Be Trusted: Steamer vs PECOTA

PECOTA

I use Fangraph’s data for most of the research I put into articles.  It has become one of the most used baseball research databases for die-hard or casual fans.  Fangraphs put out their Steamer 2019 season projections a couple weeks ago, and just with any projections they come with some scrutiny.  The other big projection system that is well followed is that of Baseball Prospectus’s PECOTA.  They use different algorithms to make their projections and can be much different that that of what Steamer projects.  This season, the Milwaukee Brewers seem to cause a major disagreement between the two.  Below are the projections from each system.  Lets just say Brewer fans aren’t too pleased with Fangraphs.

Fangraph
PECOTA

The Brewers are either viewed as a first place team or a last place team.  No in between.  The projections differ an entire 9 wins.  Who is more likely to be correct and where are the big discrepancies in player projections?

Lets take a look at the differences in player projections.  BP (PECOTA) has a different algorithm for WAR than what Fangraphs (Steamer) uses.  In this case we cannot really compare WARs at face value.  But we can get a feel as to who is a bit overvalue and undervalued compared to one another.

Lorenzo Cain is the player that the projections agree least upon.  In 2018 Lorenzo Cain produced a 4.5 WARP (same as WAR only BP’s method).  This season PECOTA is projecting him at 4.8 WARP.  In other words, they think that last season was a down year compared to this upcoming season where he will be another year older.  On the flip-side, Fangraphs projects a 3.8 WAR in 2019 which is down nearly half from his actual 2018 where he put up a 5.7 WAR!  This drop is due to fore-seeing a decrease in defensive production.  Considering much of Cain’s value comes from his excellent defense it can be understood how turning another year older might slow him down and make him slightly less productive defensively.

In terms of the other players, both projections seem to be in agreement based on how they will perform compared to the prior season.  Both see nearly a win decline for Travis Shaw, both expect Yelich to drop off from his MVP season but still be a great player, both see Aguilar to drop down closer to his 2nd half of 2018 form than his 1st half, and both see Grandal to do what hes been doing the past two seasons.

In terms of pitching, PECOTA projects Jimmy Nelson to come back strong with a projected ERA 0f 3.54 in a season where he will see limited innings.  Meanwhile, Steamer projects Nelson to pitch more innings but with a 4.21 ERA.  As a whole, PECOTA is much more bullish on the starting pitching staff specifically with regards to Nelson and Woodruff.

Overall, PECOTA projects a much better division than Steamer projects.  PECOTA has every team in the Central at or above .500 while Steamer sees both the Brewers and Pirates below.  A win total of 83 or 84 would be right in between to two and maybe seems the most logical.  Obviously there can be more moves made as the Brewers have been attached to Keuchal among other players via trade or signing.  Brewers beat the projections last season.  Can the do it again?

 

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