Shifted: The Mariners Infield Defense and Team Identity

Since the beginning of 2016, the Mariners have heavily employed a very trendy strategy: the infield shift. In the season and a half since Jerry Dipoto and Scott Servais have led the Mariners, they’ve utilized some sort of shift the fourth most in the majors. With Jean Segura’s five-year extension wrapped up, the majority of Mariners infield looks like it’s set for the foreseeable future. With this in mind, now is as good a time as any to take a look at how the Mariners infield defense has performed this season.

Early last season, I took a look at how the Mariners were changing their defensive strategies by implementing more shifts. A year ago, the depth of analysis was limited by the lack of granularity in the data. Since then, FanGraphs has greatly expanded the utility of their split leaderboards, giving us the necessary granularity to make some interesting observations. We can now apply multiple filters to a dataset, allowing us to look at how a defense performs on pulled groundballs into the shift and the various iterations of that query.

First, let’s just take a look at the Mariners overall defensive efficiency over the last three years. Defensive efficiency is simply the number of balls in play that are converted into outs by the defense—think of it as the inverse of a batter’s batting average on balls in play (with a few extra variables). In the table below, I’ve split the batted ball data into two buckets, fly balls and ground balls (we’ll ignore line drives for now), and provided a percentage of balls in play the Mariners have utilized a shift.

The Mariners defensive efficiency on fly balls has been exponentially better this season for obvious reasons, ranking second in the majors by this measure. This is even more important since Jerry Dipoto has constructed a pitching staff populated with pitchers with fly ball tendencies. More concerning is the decline in defensive efficiency on ground balls, even though the Mariners are employing the shift more than ever.

With our new ability to slice up the data, let’s take a look at how the Mariners are performing on ground balls with and without the shift employed. Below you’ll find a table with the Mariners defensive efficiency split into three buckets: ground balls hit to the pull side, hit up the middle, and hit to the opposite field.

On ground balls hit into the shift, the Mariners are performing well above league average. In fact, they’re leading the entire American League in that specific bucket (fifth best in the majors). But when opposing batters attempt to avoid the shift by hitting the ball to the opposite field or up the middle, they’re much more successful. To a certain extent, this is to be expected. The defensive shift is specifically designed to neutralize the types of balls in play the Mariners are converting into outs. But those other two buckets expose a defensive weakness.

For comparison, below is a similar table with three ground ball buckets, this time on balls in play where the shift was not utilized.

When the infield is positioned in a standard defensive alignment, the Mariners defensive efficiency is well below average in all three buckets. There may be a number of reasons for this. I haven’t examined quality of contact for any of these buckets. It’s possible that the Mariners pitchers have allowed particularly hard contact on ground balls leading to higher than average batting average on balls in play, but this seems unlikely to be the primary cause. Rather, I think the Mariners reliance on the defensive shift is covering up a lack of range on the part of their two middle infielders.

This is partially borne out in the individual advanced defensive metrics:

Neither UZR nor DRS is particularly impressed with Jean Segura’s defensive performance at short this year. His injury replacement Taylor Motter hasn’t fared much better. That’s a big reason why Tyler Smith finds himself on the big league roster and Mike Freeman is now a Dodger. The advanced defensive metrics are unsure about Robinson Cano, Kyle Seager, and Danny Valencia. Cano and Segura have each dealt with hamstring injuries this season which almost certainly affected their defensive range. I’m comfortable calling Valencia’s performance at first average and Seager’s probably fine based on reputation alone.

Aligning the infield to take advantage of the tendencies of opposing batters has maximized the limited range of the Mariners double play pairing. Consider the Colorado Rockies. The Rockies are fifth in the majors in defensive efficiency on ground balls yet they rarely employ a shift. Nolan Arenado, Trevor Story, and DJ LeMahieu are all elite defenders at their respective positions so they can get away with standard defensive alignments while still converting a huge number of ground balls into outs. They don’t have to shift as often because their infielders cover a huge amount of ground. The Mariners don’t have that luxury.

Jerry Dipoto is obsessed with maximizing the strengths and minimizing the weaknesses of this roster. With this trio of infielders installed through 2022, the Mariners will undoubtedly continue to rely on the defensive shift. Thankfully, the offensive contributions of these three players are more than enough to make up for their defensive weaknesses. With the infield set for years to come, the Mariners need to continue to focus on acquiring fly ball pitchers. This obviously maximizes the defensive strength of this roster. For better or worse, this is the team identity we can expect to watch while this core group of players is around.