Could the Cubs Defense Be Their Undoing?

The St. Louis Cardinals and the Chicago Cubs are the two most serious contenders for the NL Central title. If that wasn’t apparent coming into the season, the Pirates’ early unsteadiness should throw it into relief. While the Cardinals are the heavy favorites—as of Monday morning, the Playoff Odds report gives them a 59.3-percent chance to win the division, more than double that of the Cubs—the Cubs have a lot going for them, too. Their long-awaited offensive metamorphosis is matriculating from tantalizing possibility to tangible reality: they have the second-best OBP, second-best walk rate, and tied for the most pitches seen per plate appearance in the NL. They also have more pitching depth than any Cubs team in recent memory, though that depth has been tested by an early spate of injuries.

What the Cubs lack, though, and what St. Louis seems to have in spades, is the ability to turn balls in play into outs. Through 12 games apiece, the Cardinals and Cubs have the second-best and seventh-worst Defensive Efficiency ratings in baseball, respectively:

Team Defensive Efficiency

Defensive Efficiency is about as straightforward a stat as Baseball Prospectus offers. It’s simply the number of outs a team records on balls in play, divided by the total number of them. Thus, the table above is telling us that the Cardinals have turned a shade over 75 percent of their opponents’ balls in play into outs, while the Cubs are doing so at just a 69.4-percent rate. The difference is huge. Over the course of the season, teams put between 4,000 and 4,500 balls in play. If this gap held up over the entire season, St. Louis would record some 275 more outs on those balls than Chicago would.

Of course, the gap won’t hold. This early in the season, it’s still possible to sustain extreme team-level performances, but the long season pulls everyone back toward the center (we see how quickly things change in the early goings in just one day,  from game 11 to 12 the Cubs jumped  up four spots while the Cardinals dropped one). Last year, the best team DE belonged to the A’s (.728), and the worst to the Twins (.685). Still, that’s a difference of some 160 or more outs. We’re talking about a major effect, the kind that will determine the division if the two teams remain at the ends of the league in this regard.

Will they? It’s hard to say. PECOTA pegs the Cardinals for 17.6 Fielding Runs Above Average (FRAA) from now through the end of the season. Only the Rays, A’s, and Royals are projected to be better. It gives the Cubs a 2.7 FRAA projection, a projection that actually puts them 10th in all of baseball. Projecting defensive performance is quite difficult, not least because we have trouble measuring it in the first place, but the suggestion here is that the Cubs will rebound toward the center of the league and start getting better glove work—or, maybe, just better bounces—by season’s end.

PECOTA has to make assumptions in order to make projections, though, and that introduces the possibility that these forecasts could be pretty far off-target. The Cubs got a boost in their projection when they called up Kris Bryant last week; the FRAA system prefers his expected defense to that of Mike Olt, Tommy La Stella, and Arismendy Alcantara. Scouts seem divided on Bryant’s glove, though, and Olt has generally garnered high praise for his ability to hold down the hot corner. The system expects Chris Coghlan to provide above-average defense in left field, but the other advanced defensive measurement systems regard Coghlan as one of the worst left fielders in baseball. It appears that Addison Russell will be getting the bulk of the playing time at second the rest of the way, and his addition alone—one that is projected to bring an FRAA of 0.0 for the rest of the season—gave the Cubs nearly a four-point bump in FRAA.

The Cardinals offer a bunch of established veterans with great defensive reputations, from Yadier Molina to Jhonny Peralta to Jon Jay. Even young players like Matt Adams and Kolten Wong have longer track records than the likes of Bryant, Baez, or Jorge Soler, and those track records speak well for them. It looks like a safe bet that St. Louis will catch the ball better than the Cubs all season long. The question is whether the Cubs will be able to outslug that deficiency.