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Shifty Data: The Mariners and the Infield Shift

With defensive shift data now available to us, let's try to figure out how well the Mariners have employed the shift.

Noah K. Murray-USA TODAY Sports

Earlier this year, FanGraphs added infield shift data from Baseball Info Solutions dating back to 2010. The infield shift isn’t new, but its use has exponentially increased the last few years. In 2015, almost of a quarter of the time a ball was put in play, an infield shift was employed. With teams looking for every single competitive advantage, implementing infield shifts against pull happy batters seems to be the strategy du jour.

A couple of notes about the data:

  • It only includes plate appearances where a ball is put in play. This means strikeouts, walks, and home runs are not accounted for in the data.
  • It is broken into four different splits: all shifts, no shifts, traditional shifts (generally three infielders on one side of the diamond), and non-traditional shifts (situational shifts not covered by the definition of the traditional shift). For the purposes of this article, I’ll be using the data covering all shifts.
  • As it’s presented to us now, there’s no way to further split the shift data to determine how often a batter grounds into the shift or hits a fly ball over the shift. That means the data is a little bit muddy and doesn’t give us a full picture of how effective defensive shifts have been.

Under the previous regime, the Mariners had a mixed relationship with the infield shift. In 2012, they shifted their defensive alignment the ninth most in baseball, though those shifts only accounted for just 4.0% of the balls in play against them. But as more and more teams adopted the infield shift, the Mariners were slow to adjust to this new strategy. Here’s how the Mariners shift data has looked since 2010:


# Shifted

% Shifted






























Under the previous manager Lloyd McClendon, the Mariners stuck with traditional infield positioning the vast majority of the time. In 2015, McClendon shifted his infielders just 8.6% of the time a ball was put in play, ranking just 25th in the majors. The year before that, he shifted even less, on just 7.6% of the balls in play, though that number was the median amount in baseball at the time. You can see how eager the other organizations were to adopt the infield shift last year.

Everything has shifted this year. Under Jerry Dipoto and Scott Servais, the Mariners are employing a shift on almost a quarter of the balls put in play against them. That’s the ninth highest mark in the majors so far and it represents a massive change in strategy for the team. So, has this adjustment paid off for the Mariners?

Let’s compare last year’s shift data to the results from this year. I’ll be comparing batting average on balls in play, ground ball rates, the rate of balls hit to the pull side and up the middle, and overall batting performance, represented by wOBA. For the batted ball direction, I’m including balls hit up the middle since grounders hit that way will often be gobbled up by the second baseman or shortstop if a team is employing a traditional shift. Remember, since this shift data is only taking into account balls in play, the wOBA listed below will not include strikeouts, walks, and home runs.

To the data!

Pitcher Shifts

Last year, the Mariners severely underperformed while employing a defensive shift. Their batting average on balls in play was the worst in the majors while shifting. Opposing batters weren’t simply hitting to the opposite field either; they were beating the shift by hitting the ball up the middle. The Oppo% against the Mariners while shifting was just 22.0%, the third lowest mark in the majors, while their Cent% was the highest at 44.1%. Perhaps teams took advantage of Robinson Cano’s injury that might have limited his range up the middle.

This year, they’ve flipped the script. Not only are they shifting more often but they’re more effective when doing it. When employing a defensive shift, the Mariners are converting three-quarters of the balls in play into outs, the 7th best mark in the majors. That’s a vast improvement and much of it can be attributed to the rate at which opposing batters are hitting directly into the shift. Their 42.8% Pull% while shifting is the 6th highest rate in baseball and represents a nine point increase over last year.

Employing an effective defensive shift requires good data to determine when to shift and good communication between the pitching staff, the infielders, and the coaching staff to implement a sound strategy. Last year, there was a break down in one of these components leading a dismal performance while shifting. For whatever reason, the Mariners have employed more effective defensive shifts this year. The pitching staff has certainly benefitted from the defensive improvements—as a team the Mariners are converting 72.3% of the balls in play against them into outs, the 9th highest mark in the majors.

Next week, I’ll take a look at the batting side of defensive shifts to see if the Mariners are avoiding hitting into the shift or not.