Depth, in Detail

Yesterday, I took a look at how the Mariners and the Athletics have pursued certainty this offseason. No one can accurately predict the future so general managers try to bet on players who give them the most amount of certainty for the upcoming season. The Mariners are betting on known quantities who have a long track record of success, either at the major league level or in the organization's system. The Athletics are hedging their bets with a deep roster full of above average players.

Coincidentally, Jeff Sullivan also wrote an article taking a quick look at team depth.  In that article, he uses the Steamer600 projections to arrive at a very rough estimation for which team has the deepest roster. Here's his methodology, per his article:

There's no perfect way to do this, to my knowledge. This is just one way of doing this. For each team, I grabbed all the position players and all the starting pitchers who show up on the current depth charts. I decided to ignore bullpens, because they're a lot more variable, and bullpen depth can also look a lot like rotation depth to some extent. So, one caveat here is that relievers are excluded, but individual relievers typically aren't too important, and you can just mentally factor in that, say, the Royals have a more awesome bullpen than anyone else. It's strong and deep. Anyway.

I then downloaded the Steamer600 projections for position players and pitchers. These are the regular Steamer projections, prorated out to full seasons so that every player is put over the same denominators. Then I simply counted how many position players or starters on each team are projected for a full-season WAR of at least 1.0. A threshold had to be set somewhere, and the threshold was going to be arbitrary no matter what, so 1.0 just felt right to me. These are players you can use without killing your team. At the minimum, they're not quite good enough to start, but they're better than replacement-level.

By this method, the Mariners and the Athletics tied for fourth deepest roster in the majors (along with the Yankees). The Angels were tied for ninth while the Rangers and Astros all fell much lower in the rankings.

Jeff's methodology is pretty quick and dirty. It includes all the contributions from the projected starters at each position and doesn't include anyone below his 1.0 WAR cutoff, even if they're projected to be a starter. There's nothing wrong with this—he accomplishes what he set out to do and understands the limitations of his method.

Since I've been thinking about team depth and projections, I thought I'd take a stab at building my own team depth evaluation. It will be very similar to Jeff's method, except I'll account for the drawbacks I mentioned above. I used the depth charts on FanGraphs to determine the projected starters at each position and a nominal five-man rotation. Once I did that, the rest was just a straight sum of the remaining WAR totals for all the bench and depth players.

Before we get to the results, a few notes:

• I limited my results to just the AL West. These are the teams the Mariners are most concerned with.
• I also ignored bullpens for the same reasons Jeff did and because they skew the data a bit.
• I had to make some judgment calls when determining who was a starter. Ben Zobrist isn't listed as a starter for the A's but I assumed that he would the lion's share of time at second over Marcus Semien. For the five-man rotations, I also had to make some judgment calls but this was usually injury related. Matt Harrison, while projected to accumulate the third most WAR on the Rangers, probably won't pitch this year and may retire due to his back injury.
• When adding rotation depth, I only used projections for players if they were projected as starters. This means players like Erasmo Ramirez, Jesse Chavez, and Drew Pomeranz weren't included in my totals.

To the graph!

The Athletics lead the AL West with 11.2 bench/depth WAR. This doesn't come as a surprise. The Athletics have a deep roster that passes the eye test and is reflected in these numbers. But, the Mariners are right behind them with 10.8 bench/depth WAR. On the surface, the Mariners may not seem like they have a deep roster but Steamer is pretty high on Jesus Montero and Ji-Man Choi, projecting over 1.0 WAR from both of them over 600 plate appearances. Chris Taylor (assuming Brad Miller is the starting shortstop), Taijuan Walker, and Justin Ruggiano all push the Mariners' total up the chart as well.

I think the real surprise is how close the Astros come to matching the Angels in bench/depth WAR. The Astros have a deep outfield, with two players who are projected to be worth more than 1.0 WAR on their bench and two more that are projected to be better than replacement level as extra depth in the system. They've also accumulated some depth at middle infield in case Jed Lowrie breaks down again. The response to the Astros' rebuilding plan swings from "LOLZ Astros" to "Wow, Astros," but I think we need to give Jeff Luhnow some more credit. He's building a deep roster filled with cost controlled pieces that could be ready to contend as soon as 2016.

On the other hand, the Angels are moving more and more towards a stars and scrubs approach to roster construction. Their roster is pretty top heavy and doesn't have much depth past their bench pieces. The Rangers also have a pretty top heavy roster and they're in even worse shape than the Angels. It's no wonder they completely collapsed last year after dealing with a plethora of injuries across their roster.

Yesterday, I observed that the Mariners roster isn't built to withstand a number of things going wrong. I still stand by that comment but this exercise gives me a bit more hope. The Mariners' roster certainly isn't as deep as the Athletics but, according to Steamer, it's not far behind. Adding a few more minor league signings and your random non-roster invitees will help the Mariners fill the gaps in their depth. It looks like the AL West is shaping up to be the most competitive division in the league yet again.