Assessing the Cubs’ Defense in a Metric-less World

If you have your ear to the ground, you might be hearing the beginnings of a seismic shift in baseball analytics. No—it’s not the mythical “bullpen revolution” that so many have seized upon as the privileged narrative of mainstream analytics writing. Truth be told, that “revolution” is merely the loudening machinations of the long march toward specialization, the narrative a product of a search for meaning in an era when baseball, The Game, feels its most meaningless. The rumblings that you hear are, rather, growing resistance to the stunted defensive metrics that grew out of the last era (or, possibly, two or three eras ago).

Can you feel it? It finds a voice in the pages of Baseball Prospectus, at the time overshadowed by the World Series. It’s whispered in hushed tones by player evaluators in our public analytics community. Questions about our evaluation of players’ defense are growing, and good baseball minds are picking apart assumptions upon which we’ve built defensive metrics and evaluation for a decade now. The truth is, we simply don’t know the usefulness of the metrics we currently enjoy, and it’s increasingly frustrating to both watch analysts tout defensive metrics as gospel, and to come up short every time in describing a player’s defensive ability. How can we pin a number, a run value, to a player’s defensive performance if we don’t even know the degree to which positions are differentiated or how different skill sets translate to positional changes, if we don’t have enough data involving position players of varying skills switching positions?

So, when I set out to write about the Cubs’ holistic 2017 defensive performance—not only breaking down individual player performances, but using my powers of almighty hindsight to critique how those players were deployed and how they fit together—I immediately confronted a problem. Am I to take these defensive metrics as a starting point? Should I throw them out completely and use my eyes and gut to assess this team’s play in the field? Well, as my player evaluation chops are not that of others in the baseball writing community, I’ve decided upon the former. The metrics are where I’ll begin, but I imagine I won’t hover around them too long before taking a path that leads me elsewhere.

First, then, I’ll present a slate of defensive data, the major metrics’ numbers for the Cubs 2017 defense compared to the rest of the league and to the 2016 iteration of the Cubs. Team rankings are in parentheses. Keep in mind that these metrics all use different scales, so you should compare across columns, not down rows. PADE is centered at zero.

2017 Cubs 2017 League Avg. 2016 Cubs

Defensive Efficiency (DE)

.715 (6th)


.745 (1st)

Park Adjusted Def. Efficiency (PADE)

1.41 (6th)

6.38 (1st)

Defensive Runs Saved (DRS)

30 (5th)


82 (1st)

Defensive Runs Above Average (DEF) 21.8 (6th) 28.1

69.0 (1st, nice)

That passes the sniff test. The 2016 Cubs were a historically good defensive unit by most measurements, and human evaluation critical consensus agreed. There were, and are, some concerns about the exponentially higher numbers the Cubs put up in PADE, a stat that is expressed as the percentage of balls in play that a team turns into outs over the average team (i.e. the 2016 Cubs converted six percent more balls in play into outs, adjusted for park factors, than the average team). But, across the board, the 2016 and 2017 Cubs rate consistently. The Cubs were not the top defensive unit in MLB this year, but they were still among the five or six best.

 The Cubs replaced good defensive players with not-as-good defensive players in a few positions.To me, this makes sense. But we’re here to figure out why, and there are a few factors at play.

  1. The Cubs’ incumbent defenders were not as good this year, due to age or otherwise, as they were in 2016.
  2. Joe Maddon deployed defensive alignments that exposed individual weaknesses, rather than selecting configurations that would shore up those weaknesses.

Normally, the first factor would be relatively easy to analyze, but the ways in which Maddon platooned his players varied greatly between these two years. Most simply, Dexter Fowler, Jorge Soler, Miguel Montero, David Ross, and Matt Szczur found themselves supplanted by a combination of Albert Almora, Jon Jay, Ian Happ, Kyle Schwarber, and Willson Contreras. I’m fairly confident that the center field performances of Almora and Jay were slightly worse in overall run prevention than Fowler’s 2016: Fowler had a career year defensively, mostly due to changed positioning, and Almora looked slightly off this season from the stellar defender we have come to know. There’s a small drop off there, even if we don’t expect that to continue going forward with Almora demanding more playing time.

In left, we have less of a downgrade than one might expect. Schwarber is a poor defensive outfielder no matter how you slice it, but Soler, Contreras, Szczur and the others who crewed the position in 2016 were only slightly better. On the days when Happ or Jay found himself in left this year, the Cubs were probably deploying their best defensive outfield with Almora and Heyward in center and right. Schwarber did not quell any fears that fans might have harbored coming into 2017, but he will likely remain in left, barring a trade.

Behind the plate, the 2017 Cubs were markedly different than the 2016 iteration despite featuring two of the same players most of the year. In their World Series campaign, the Cubs relied on Montero and Ross to be impeccable pitch framers, pitch blockers, and game callers, while the rookie Contreras played primarily in left and learned to frame and handle pitchers at the major-league level. Contreras was a good defender at catcher this year, mostly due to his stellar arm, but his pitch framing and other defensive attributes improved.

Slight dips in production in both center and left, plus a different look behind the plate, probably contributed quite a bit to the Cubs’ fall from the slickest defending team to merely a good defending team. Players like Ben Zobrist, Kris Bryant, and the previously mentioned Almora played at levels lower than that one expects of them, compounding the personnel changes’ effects. Zobrist played like he was 50 years old this season on both sides of the ball, despite his confounding Gold Glove finalist status, and was a detriment to the Cubs at second base and in the outfield. Bryant, who grew throughout his first two major-league seasons at the hot corner, took a minor step back in his third year; while the reigning MVP found himself at third more often with a crowded outfield situation this year, his throwing and his hands were not as assured. The pair of Zobrist and Bryant garnered a sizeable portion of the Cubs’ defensive innings in 2017, and so their setbacks loom somewhat large.

Which brings us to our final factor, and the one on which I have harped for two seasons now: optimal defensive alignment. While his major-league-best infield is set in stone, Joe Maddon showed little concern with outfield defense, choosing to punt on center and left fields more often than not in order to gain some advantages at the plate. Of course, that’s often a sound strategy. However, Happ playing center field, Zobrist playing in either corner, or Schwarber playing in left all sink the outfield defense, and if two of those players are in those spots, then even Jason Heyward cannot save them. Few times did we see the Jay-Almora-Heyward alignment that would likely be the optimal defense, even with balls flying off the bat in the air at an alarmingly high rate.

Luckily, Heyward, Addison Russell, Javier Baez, and Anthony Rizzo remained Gold Glove-caliber defenders, and if half of your defense plays at that level every season, your team is working with a much-envied advantage. This, clearly, explains the Cubs’ position in the above defensive rankings. The Cubs’ defense was tops in the majors in groundball defensive efficiency this year, as they had been in 2016. On flyballs, however, the Cubs performed only adequately: they ranked 16th in 2017, sliding 15 spots from their first-place mark in 2016. With the league average flyball rate at its highest since 2011, outfield defense takes on increased importance. However, there also exists the larger trend toward fewer balls in play league-wide, with strikeouts and walks and homers all on the rise—perhaps Maddon and the front office decided that sacrificing defense for offense in 2017 was increasingly acceptable.

A step back from record heights in defensive performance is nothing to be ashamed of, and one would have been foolish to expect the Cubs to repeat their 2016 vintage. That doesn’t excuse or explain the reasons for the Cubs’ defensive downturn in 2017, however, and the metrics only suggest what might have happened over these two seasons. Defensive assessment is tricky; it will remain tricky, even if better analytics are developed and more incisive minds prevail. By breaking down these specific differences—by finding variations in performance from year to year, by seeing how the Cubs’ defensive players aided or sunk each others’ performances—we can still come to a basic understanding of how the Cubs defense functioned without shackling ourselves to methodology built on a crumbling foundation.

Lead photo courtesy Dennis Wierzbicki—USA Today Sports

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1 comment on “Assessing the Cubs’ Defense in a Metric-less World”

This is fascinating. Well done, well researched, well presented. Thanks much.

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