FIP Check: By at Least One Measure, the Cubs Have the Best Rotation in Baseball

You wouldn’t know it from looking at them, but the Cubs are right in the conversation of the best starting rotation in baseball. Not bad for a group comprised of an overpaid bum with a case of the yips, a workout freak with honey in his beard, a retread they flipped and then re-signed, a guy who looks — and throws — like a high schooler, and a revolving door of extras from Central Casting that has now been replaced by a soft-tossing geriatric.

No, this group isn’t going to be mistaken for the 90’s-era Atlanta Braves, but they’re putting together a pretty nice season nonetheless. By the most popular measure of pitching performance, this staff has been quite good, if not great. Their aggregate 3.42 ERA is 6th in MLB, though it’s bested by both the Cardinals (2.84, 1st) and the Pirates (3.36, 5th). Their batting average against is a paltry .236, which ranks them 4th in all the land.

Contrary to their past performance, this year’s crop of Cubs starters has limited the walks, allowing them at a rate of 5.9% that has them ranked 5th. And what’s more, they’re striking 23.5% of the batters they face, good for 2nd place behind only the Indians. Likewise, the Tribe (17.7%) is the only team with a better K-BB mark than the Cubs’ 17.6%. The case for this being a pretty darn good unit is coming together nicely, no?

Well, it’s about to get even stronger. That’s because the Cubs look a lot better when we strip away some of the factors the pitchers can’t control. ERA is popular because it’s been around for a long time; it’s the McDonald’s of pitching stats. You turn to ERA when you need a quick fix or when you’re too lazy or in too much of a hurry to look further. But FIP is fast becoming a more acceptable way to measure pitchers’ performance.Why? Well, let me let FanGraphs explain it.

Fielding Independent Pitching (FIP) measures what a player’s ERA would look like over a given period of time if the pitcher were to have experienced league average results on balls in play and league average timing. Back in the early 2000s,research by Voros McCracken revealed that the amount of balls that fall in for hits against pitchers do not correlate well across seasons. In other words, pitchers have little control over balls in play and assuming short-term fluctuations in BABIP are attributable to the pitcher is likely incorrect. McCracken outlined a better way to assess a pitcher’s talent level by looking at results a pitcher can control directly: strikeouts, walks, hit by pitches, and home runs.

FIP is a measurement of a pitcher’s performance that strips out the role of defense, luck, and sequencing, making it a more stable indicator of how a pitcher actually performed over a given period of time than a runs allowed based statistic that would be highly dependent on the quality of defense played behind him, for example. Certain pitchers have shown an ability to consistently post lower ERAs than their FIP suggests, but overall FIP captures most pitchers’ true performance quite well. For this reason, FanGraphs’ version of Wins Above Replacement (WAR) for pitchers is based on FIP rather than on ERA and even analysts who prefer a different method of determining WAR find FIP to be extremely useful and informative.

Think of it this way: if Jake Arrieta gives up a hit that most other right fielders would have gotten but that Jorge Soler can’t reach due his circuitous route to the ball, FIP doesn’t ding Arrieta as ERA would. If a duck-snort drops in or a swinging bunt somehow stays fair, those don’t count against the pitcher. I’m sure there are some old men out there shaking their fists at the “but he should’t’ve allowed the contact in the first place” cloud, but c’est la vie.

The Cubs rotation has a 3.25 FIP that puts them in a tie with the Dodgers for the best in baseball. Of course, lurking right behind them are the Pirates (3.26, 3rd) and the Cardinals (3.28, 4th), which basically tells you that the NL Central features the best pitching in the game, at least from a divisional standpoint. Just to validate that point in quick-and-dirty fashion, I calculated the aggregate scores of each division based on FIP rankings.

Other than the Dodgers, the NL West is pretty weak and came in tied with the AL Central for the worst overall total of 86. The AL East racked up an 84, the AL West a 78, and the NL East a 75. But on the strength of three top-5 FIP teams, the NL Central cruised into first place with a total score of 54. Now, that’s a pretty cool little factoid. Trouble is, that and a dollar will get you two tries at a claw-grabber game.

What it does tell us is that it’s going to be really tough to gain ground in the division and/or on the Wild Card when all three teams involved are lumped so closely together. Last night’s 5-0 victory over the Pirates adds some confidence though, to be sure. Of course, there’s also the possibility that the Cubs will end up having to beat out the Dodgers, the other team with a strong claim to rotational supremacy for a playoff spot.

As we just saw, those teams are deadlocked in FIP, but the Cubs fall away from the Dodgers a bit once we delve into xFIP (a regressed version of FIP that replaces how many home runs a pitcher has allowed with how many he should have allowed based on how many fly balls he’s allowed while assuming league-average HR/FB ratio) and SIERA (which “attempts to explain why certain pitchers are more successful at limiting hits and preventing runs”).

Los Angeles has a 3.15 xFIP and and 3.26 SIERA, both of which just edge out the Cubs’ marks of 3.20 and 3.29. So the Cubs might not have the best overall starting 5 in the majors, but it’s not a stretch at all to say that they’ve got the second-best. In that light, it’s not surprising that they didn’t offer up top prospects for a pricey deadline addition when Dan Haren does actually make them stronger than what [insert name here] has in that spot throughout the season.

Much has been made of the Cubs’ offensive struggles, a topic that may have forced many of us to overlook just how good this staff has been all season. We’re deep enough in at this point to say that these numbers accurately reflect what this rotation is, and it’s reasonable to believe that they could yet get better. That’s very good news when you consider that the offense could/should improve as well.

Having a rotation that is performing at this level provides a significantly larger margin for error than what the Cubs have experienced in the recent past, and that’s a very good thing for a group of hitters that has yet to really come into its own. It’s dangerous to walk around looking through binoculars, but envisioning another top-end arm joining this group as the bats mature at the same time has me salivating.

In the meantime, however, the Cubs need to pocket the field glasses and just put one foot in front of the other as they walk what is sure to be a pretty narrow and pock-marked path to October. Having a surprisingly good group of starting pitchers should help them to do just that.