You cant huck a paper airplane in Wrigley Field without hitting something the Cubs are the best at. They have the National Leagues best offense (by OPS+), the NLs best pitching (by ERA+), the NLs defending Manager of the Year and, since the trade deadline, arguably the NLs best bullpen. Their baserunning -- well, their baserunning is only average, which is hardly enough for the Giants to build a battle plan around.To really appreciate the Cubs, though, background all those bests and focus on their defense. This will not be easy. Most great defense is of the slow-and-steady-wins-the-race variety, a ragout of positioning, lineup decisions, first steps and fundamentals. Its body awareness, its balance, its torque, its internal clock. Its not a screaming liner, and its not 98 mph. Its the left fielder who takes two steps to his left before the pitch is thrown. Its cutting sodium from your diet. Its changing your oil on schedule. Its starting your 401(k) right out of college. It adds up.The Cubs have converted 74.5 percent of balls in play into outs this year, which is what Baseball Prospectus calls Defensive Efficiency. (Rephrased: Opponents are hitting .255 on balls put in play against the Cubs.) Thats not just the best in baseball this year. Adjusted for era, it might be the greatest defensive season ever, with the gap between the Cubs and the second-best team this year topping the spread between the next best and the 27th best.1. Cubs, .745 2. Blue Jays, .717 ... 27. Mets, .692Its been 34 years since a team converted balls in play at a higher clip than the Cubs, and that was when the league as a whole hit 15 to 20 points lower on balls in play than modern players do. No team since at least 1950 has converted a higher percentage of outs, relative to the rest of the league, than the Cubs just did:It doesnt matter how you hit it. The Cubs -- a team with only one Gold Glove winner on the roster, a team that shifts less than any in baseball -- are better than any other club at converting ground balls into outs (80.1 percent), the best at converting fly balls into outs (94.1 percent) and the best at converting line drives into outs (43.5 percent). They do this despite allowing an exit velocity that is almost exactly league average, and an exit velocity on grounders that is harder than league average. They have allowed roughly 110 fewer base hits than they would have if they had the Blue Jays defense -- if they had, in other words, merely the best defense in the American League.But, again, we run into an appreciation problem. Some of these 110 were this.But many -- most -- will look to us out here like routine baseball. To appreciate what the Cubs do, then, we must understand what well see in even the most banal highlights.Anthony Rizzos FootworkIf you know one thing about Rizzo as a ballplayer, its that hes a great slugger. If you know a second, it might be that he crowds the plate like nobody else, crowding into the territory that a pitcher would normally consider his own -- and suffering the bruises for it. If you know a third thing, it might be that he spends so much time in the stands that he should count toward paid admission, making terrifying plays like this one, or this one, or (hold me) this one. Rizzo is brilliant, but hes also fearless.Heres a fourth thing: Since 2014, no National Leaguer has handled more difficult throws than Rizzo, according to Baseball Info Solutions. He has saved his infielders 98 times, shy of only the Royals Gold Glover Eric Hosmer. We might credit it to the same fearlessness he shows toward inside fastballs and awkward landings.If youre watching the highlight embedded above -- a fairly unremarkable play (especially on his end) from last years National League Championship Series -- watch his back foot closely at the 0:37 mark:This is not how first basemen are taught to do it. Most will wedge their foot up against the flat face of the bag, peeling off just a sliver of the white canvas. The Milwaukee Brewers Major League Baseball Manual (published in 1982) teaches first basemen to prop the back foot right up on the edge of one corner. See, for example, Joey Votto:or Eric Hosmer:Rizzo does it differently. He puts his foot all the way up on the pillow, maximizing the surface-to-surface contact.Watch him play first base for long and youll see that he considers the bag his property, just as he considers the inside corner and the first two rows of the Club Box his property. Instead of stretching for errant throws, he repositions his feet and reorients his body so that he can square the ball up, even at what sometimes seems to be incredible peril and total disrespect for the baserunner:Theres a reason first basemen dont do it this way. Believe me from experience, says Tommy Lyons, a first baseman who plays independent-league ball, a cleat to the cankle, or Achilles, is no joke. But there might also be a reason to do it: With a firm position on the bag, Rizzo has more room to move without losing contact with the base, an especially useful consideration now that replay reviews ensure the slightest disconnection will be noticed.Javier Baezs HuntingIn early September, Jesse Rogers wrote about Baezs tagging swagger, especially at second base:Baez said he learned a long time ago how to apply the quick tag. It began as simply waiting as long as possible before reacting to the ball in order to deke the runner. A quick catch and then tag was needed to complete the play. Soon enough, it became part of his DNA as a ballplayer.When I was little in Puerto Rico, they showed me how to get early to the bag and act like nothing was coming, then at the last minute, catch and tag, Baez said with a smile. It kind of forced me to be quick at the last second ... I just kept working at it and kept getting better and better at it.Theres nothing all that special about the tag in the highlight we embedded, but I love the force Baez uses. I love how he pursues the runner and almost spears him with the glove, knocking him all to pieces and having to go pick him up. Heck, Ill just say it: I love it as metaphor.Baez, more than anybody youll see this October, hunts after outs. There was a play this season where Baez was not assigned to cover second base on a stolen base attempt. The catchers throw was awful, so bad that Baez, backing the play up, couldnt get to it, and it went into center field. As the baserunner, Keon Broxton, got up and started to go to third, glancing to find the ball, Baez deked as though he had the ball. Its not uncommon to see middle infielders deke baserunners in situations like this, but Baez sales job was extraordinary: He smacked his glove, spun his whole body around, arm raised and cocked and ready to throw; he even started to run at the baserunner. It didnt work! Broxton saw the ball in center field and advanced to third. But Baez does that sort of thing all the time, cutting angles and anticipating daylight where he can steal an out.Indeed, its not even the quickness that most stands out to me about his tags. Well, maybe it is. But not exclusively that. Baez often doesnt do what you expect from the guy covering second base on a stolen base attempt -- he doesnt wait for the throw, catch it and lay it down in front of the bag where the runners fingers are stretching for safety. Rather, Baez reaches out in front of the bag to catch it and then drops the tag on the body or the head of the baserunner. He shaves a few feet off the catchers throw and he gives himself a bigger target to slam a tag onto. He puts himself in position to tag the most elevated part of the baserunners body, which is usually up the baseline -- where a foot-first sliders torso and head are, or where a headfirst-divers shoulders are elevated or his legs kicked up in the air. Like in this play, maybe my favorite Baez tag: Jonathan Villar is safe, by plenty, but you can see how Baez is 1) pulling the tag down before hes even caught it, 2) swiping it toward Villars rib cage, rather than putting it down in front of the bag and 3) taking that step forward so that his feet are now directly in front of the bag, blocking Villars hands from a direct path to second.Baez might be the most important part of the Cubs defense, moreso even than the Gold Glove-caliber shortstop Addison Russell. He is a superutility player who is not just passable but exceptional wherever he goes, which has led Cubs manager Joe Maddon to create what is essentially a defensive platoon -- a platoon based not on who is pitching for the other team, but who is pitching for the Cubs. Maddon puts Baez wherever he thinks the ball is going to be hit most often. So when Jon Lester starts Game 1 of the NLDS, theres a decent chance that Baez will be at third. Lester, the lone lefty in the Cubs rotation, faces nearly 80 percent right-handed batters, compared to 50 to 60 percent for the rest of the Cubs starters. Almost all batters tend to pull their ground balls, and thats especially true of right-handers facing Lester:Add to that Lesters trouble throwing to bases, which makes teams more likely to bunt against him, and which requires the third baseman to cover more ground. When Lester is on the mound, then, the question Maddon asks himself -- Where is Baez more likely to be hit to? -- is easy to answer.The straight-up defenseIn 2010, the Tampa Bay Rays?-- then managed by Maddon -- shifted more often than any other team, accounting for about 10 percent of all the shifts (on balls in play) in the majors, according to Baseball Info Solutions. In 2011, they led the majors again, and in 2012, and in 2013 Maddons Rays were second, just 40 shifts behind the Orioles.This year, with the Cubs, Maddon called for fewer shifts than any other manager, 50 fewer than the 29th-place Miami Marlins and almost 1,500 fewer than the Houston Astros. The Cubs accounted for just 1.4 percent of all shifts across the majors.So what changed Maddons mind about this seemingly progressive tactic? Maybe nothing. With the exception of 2014, when the Rays nearly doubled their shift frequency, Maddons teams have been fairly steady from year to year. Its the league that has changed around him:Maddon has been asked why he doesnt shift as much as he used to, and he usually doesnt say but I do. Why give away your strategies, after all. Instead, he offers answers that are not very convincing. For instance: He also said that while many lefties hit the ball in the air to right field, ground balls go to the left side, which makes shifting more dangerous. This is pretty much exactly wrong. Most hitters pull grounders and go to the opposite field on fly balls. But Maddons boss, president of baseball operations Theo Epstein, offered an explanation that does make some sense: When you shift you risk turning hitters into better hitters than they otherwise would be. Youre opening up holes and encouraging good hitters to use the whole field. That is, by incentivizing hitters not to pull the ball, shifting defenses convince hitters to actually do the thing a lifetime of coaches have been telling them to do: stay back and use the whole field. (For a great case study on this, see Mike Moustakas, whose offensive breakout came when he started trying to thwart the shift -- not because he was hitting ground balls through vacated infield holes, but because he started banging hard line drives into left field.) Russell Carleton at Baseball Prospectus has found that, in aggregate, the leagues tens of thousands of shifts produce only a modest benefit, once all offensive outcomes are included in the results.So: Imagine you have 1,000 scratchers, and you know that in the aggregate they are going to win you $1,000. Does that mean each of them is go