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A rough win projection for the Mariners

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Using ZiPS and Steamer, let’s build a win projection for the Mariners.

MLB: Texas Rangers at Seattle Mariners Joe Nicholson-USA TODAY Sports

Yesterday, FanGraphs released the 2018 ZiPS projections for the Seattle Mariners. Along with Steamer and PECOTA, ZiPS is one of three highly regarded projection systems publically available. I’ve written some form of this post four years in a row now, so you probably know what to expect. But for the first time since I’ve been writing these articles, ZiPS is actually more optimistic about the Mariners than Steamer.

First, let’s get all the details out of the way. No projection system is perfect. But with more data and different projection models, we can become more confident in our assumptions and estimations. ZiPS doesn’t produce projections based on projected playing time, so we have to scale them to begin to compare them with Steamer. I’ve scaled them using the projected playing time found on the FanGraphs depth charts.

As I mentioned in the opening paragraph, this is the first year I’ve been doing this where ZiPS has spit out a win projection more optimistic than Steamer. Traditionally, ZiPS has been the most conservative projection system of the big three. Using raw data from both projection systems, I built a rough win projection for the Mariners using the BaseRuns formula. I’m using the most basic form of the formula since I’m limited by the input data I can scrape from FanGraphs—this might result in a small discrepancy with the published win projection on FanGraphs but I’m working with what I’ve got. Calculating expected runs scored and runs allowed for the Mariners allows me to input those numbers into the PythagenPat formula to come up with a final win projection.

2018 Win Projection

System W L W% RS/G RA/G
System W L W% RS/G RA/G
Steamer 79 83 0.489 4.69 4.80
ZiPS 83 79 0.512 4.52 4.41

Steamer is more bullish on the Mariners offense than ZiPS is, but the biggest difference between the two projection systems is how they view the Mariners pitching staff. There are just four pitchers whose Steamer projection is better than their ZiPS projection, and only one of those four (Felix Hernandez) is projected to pitch more than 15 innings next year. The Mariners expected runs allowed calculated via ZiPS compares favorably to the expected runs allowed Steamer projects for the Red Sox or the Rays. That’s not too bad.

Of course, reality likely lies somewhere in between the two projections. But seeing a projection that’s bullish on the Mariners pitching staff could explain why there hasn’t been any urgency to sign another starting pitcher. Would signing another starting pitcher help the Mariners? Most likely. But you can almost see why Jerry Dipoto is content standing pat while waiting out the free agent market.

On the offensive side, Steamer has better projections for Robinson Cano and Nelson Cruz, two key players for the Mariners. Cruz in particular seems to be difficult to predict due to his advanced age. My guess is that ZiPS heavily penalizes him based on his age and the odd career path he’s had. Below is a chart showing the difference in projected WAR for each player on the Mariners roster.

Projecting the current roster for 79-83 wins in 2018 seems pretty fair. To reach the high end of their projections, they’ll need a lot of things to go right. Of course, a lot of things went wrong last year and they still hung around .500 for most of the year. All that bad luck has to run out sometime, right?