Take a trip with me, back to a magical time where (almost) all teams had hope for the coming season. The offseason was winding down and we were more than ready to sit down for some Spring Training and whet our appetite for the banquet of bona fide baseball to come. Back in that simpler time, we took a look at the Cubs’ offseason and declared it a resounding success. That’s not particularly strange, pretty much everyone did the same thing. The Cubs made smart offensive and defensive upgrades throughout their lineup and became deeper than they already were. So, you know, very deep.

They didn’t really do much to beef up their rotation other than signing John Lackey to take the place of the Dan Haren, Travis Wood and Tsuyoshi Wada (and more) merry go round they used last year. Not that they necessarily needed to do much. After all, this was a team that whose rotation led the league in fWAR, was 3rd in ERA, 1st in FIP and 1st in WHIP. If you were skeptical of the Cubs’ decision to stand pat other than adding Lackey, well, the Cubs were right and you were wrong, as the rotation of Jake Arrieta, Jon Lester, Jason Hammel, Lackey and Kyle Hendricks has been doing pretty well. The Cubs are 1st in fWAR, 1st in ERA, tied for 1st in FIP and 1st in WHIP.

That Arrieta is pitching well should surprise exactly no one. Fresh off winning the Cy Young last year, he’s continuing to do more or less what he did that won him the award. We all know that win-loss record is a terrible way to evaluate a pitcher’s talent level, but the fact that Arrieta took his first regular-season loss in nearly a calendar year at the beginning of June is impressive nonetheless. He’s 6th in the MLB in fWAR (2.6). By bWAR (3.0 WAR), he’s neck and neck for the lead among NL pitchers ahead of him (if you disallow the utterly unreal season Clayton Kershaw is having, obviously). Speaking of Kershaw, he’s the only pitcher in the MLB with a better ERA (1.58) than Arrieta (1.86).

To be fair, Arrieta isn’t pitching as well as he did last year, at least in in terms of one peripheral. His walk rate is up by almost one per nine (2.90 this year vs. 1.89 in 2015). As you can tell from his ERA, though, the walks haven’t ended up hurting him that much. His FIP (2.59) is over half a run higher than his ERA, but this was also the case last year (when it was 2.59) over a whole season. Not to mention that his FIP is good enough for 5th in MLB. His BABIP this season is .241. Low, to be sure, but last season his BABIP was .246 and his career BABIP is .241, thanks at least partially to him being the “king of weak contact”.

Moving on to Lester, he’s just behind Arrieta in 3rd place on the leaderboards when it comes to ERA (1.89). With 2.4 fWAR, Lester is already about halfway to his 2015 total (5.0). By bWAR (3.1 in 2015 and 2.6 this season), he’s almost there. He’s throwing his fastball more than he has since his earliest seasons with Boston, and it’s working. He’s continuing to strike out about a batter an inning (8.93 K/9), as he’s done for the last couple of seasons. His walk rate was already very good over the last two seasons (1.97 BB/9 in 2014 and 2.06 BB/9 in 2015) but now it’s excellent (1.79 BB/9). He is, however, sporting an even bigger gap than Arrieta between his ERA and FIP (2.85). Like Arrieta, Lester is also sporting a criminally low .259 BABIP, but, unlike Arrieta, Lester’s is significantly lower than his own career BABIP (.299).

While Lackey may not have seemed the most inspired signing at the time it happened this offseason, he has been pitching well, not unlike all the other Cubs' starters. You can argue about the amount Lackey is being paid and whether he’ll keep this up through the end of his contract next year when he’s 38 (or perhaps 39 if the Cubs go deep into the postseason in 2017), but you can’t argue with the results he’s been getting. His 2.66 ERA is good for 9th in MLB and thus the 3rd entry in the top 10 for the Cubs. His FIP is a smidge higher at 2.99.

Lackey is walking about the same number of batters as the last couple seasons (2.15 BB/9 in 2016 vs. 2.19 in 2015 and 2.14 in 2014). He’s striking out batters far more than he ever has before (27.1 K% v. a career average 18.9% and a previous high of 22.3% in 2005). He’s been generating more whiffs on his slider than recent years. Lackey’s BABIP? .255, well below his .304 career average.

Hammel may be pitching in the 5th spot in the rotation, but he’s sporting a better ERA (2.26) than Lackey, good for 7th in MLB. With a 3.55 FIP, Hammel does have the biggest gap between his FIP and ERA among the five starters for the Cubs. He’s striking out less batters and walking more than the last couple of years, so there’s certainly the possibility that his ERA gravitates closer to the mid-to-high 3 ERA pitcher he’s been the past couple of years, but we’ll have to wait and see. Oh, his BABIP? .250 this year vs. a career number of .301.

Now that we’re discussing the final Cubs pitcher in the rotation, we can finally move out of the top ten ERAs in the MLB, all the way up to… 21st in MLB. Kyle Hendricks, come on down! His 3.05 ERA pairs up with a 3.30 FIP.  That FIP is pretty much the same as his FIP over the last two seasons (3.32 in 2014 and 3.36 in 2015). As with all the other Cubs' starters, he’s shaved his BABIP down this season (.244 this year vs. .278 for his career).

I know we’ve been hammering the point home, but the Cubs' starters all have very, very low BABIPs. The team’s BABIP is .250 (.250 for all starters and .251 for relievers). That is an impressive feat with over a third of the season in the rearview mirror. As August Fagerstrom at Fangraphs pointed out the other day, it’s actually beyond impressive, it’s historic and, if the Cubs maintain that BABIP the rest of the season it would be the best team BABIP since 1961 (and not even close). Furthermore, even if Cubs pitchers allowed hits to fall at the normal rate this season (.295 BABIP), they would still be in the upper echelons of the past 55 years.

We mentioned before what the Cubs had done to upgrade their defense over the offseason. It turns out that Justin Heyward is a good defender. Newsflash!!! But Heyward wasn’t the only defensive upgrade and, in case you needed proof, there are stats, lots of them! The Cubs lead MLB in UZR (26.1). They lead MLB in defensive efficiency (.733). They are second in DRS (36) behind only the Giants. The Cubs aren’t shifting as often (or at least as much) but they are doing it very effectively (if you didn’t click on that link about BABIP before, read Fagerstrom’s article, which discusses the seriously effective shifting the Cubs are doing). The Cubs were a very good defensive team last year, but they’ve gone from being very good to being the best, and that is certainly helping the rotation.

Regardless of how good the defense is, there’s likely some luck going on, but that’s just the way things work. There’s also been some luck in terms of injuries. Through over a third of the season, the Cubs haven’t given a single start to another pitcher outside of the five we’ve been  discussing. On the other hand, by their Pythagorean record or Base Runs record, the Cubs would have won an extra 4 or 2 games, respectively, so in some ways they’ve actually been unlucky, believe it or not.

So, yeah, the Cubs’ rotation is really good. There haven’t been any huge declines but they’ve all been pitching better than you would expect based on their raw numbers. The defense is certainly helping the Cubs pitchers’ cause and maybe there’s some catcher magic going on. Whatever they are doing, if they keep on doing it, this team is going to be scary come October. And that’s even without the possibility of the Cubs upgrading their rotation, as they have hinted they might do, even if it’s going to be brutally expensive. If they do that, they could be even scarier. Which is, you know, pretty scary.