It has been said that something as small as the flutter of a butterfly’s wing can ultimately cause a typhoon halfway around the world – Chaos Theory

Sometimes, a small piece of knowledge can mean a lot. Especially in baseball, the butterfly effect can reverberate from one stat into the game as a whole.

A couple weeks ago, Michael Barr had a post on FanGraphs that had one of those “Year of the” innocuous headlines that put it in the long list of declaratory posts. We’ve heard for years about the year of the pitcher, right.

But Barr’s piece was about reliever whiffs, and he started by pointing out that 2012 featured five of the top ten strikeout rates by qualified relievers over the past five years. This season, Aroldis Chapman, Craig Kimbrel, and Kenley Jansen are showing three of the top four strikeout rates over that time span.  They’re striking out over 40% of the batters they are facing! No single season has had as many 40% strikeout rates as this season. It’s pretty intense.

It’s not just the top of the pile, though. All relievers have a strikeout rate of close to 23% this season, and that’s up steadily from closer to 20.5% in 2008. The march has been impressive. See Barr’s visual:

That seems like it’s an actual trend.

In real baseball, we know a little bit about why this is happening. Pitching staffs are larger, and pitchers are being used in shorter stints that allow them to throw faster and take more advantage of their handedness in platoon matchups. Perhaps the real butterfly in this effect was the moment that the baseball transitioned from the 24-man roster to the 25-man roster? That change — achieved some time after 1986 — allowed 13-man pitching staffs to become the norm. Then we should take notice that the last CBA allows for 26-man rosters in day-night double headers, and the slippery slope begins. Won’t a reliever make the most sense for that 26th man, after all?

In real baseball, this might be the slide towards 15-man pitching staffs made up only of relievers — some long, some swing, some platoon-advantage only, some high-leverage, but all relievers. That would be one heck of a typhoon.

But let’s bring this back to fantasy baseball, why don’t we. There are two (somewhat contradictory) effects that are hidden in this finding of Barr’s.

The first is related to the shorter stints from pitchers. When, after the 2011 season, John Autin at High Heat Stats Blog pointed out that the length of the average save was dwindling — down from 1.54 IP/save in 1961 to 1.006 IP/save in 2011 — I facetiously responded that the real closer of the future was Dennys Reyes, since the portly lefty had pitched in four games in 2011 and only gotten six outs.

But we digress. The relevant effect that this has on fantasy is that the peripheral advantage that a closer has over starters has been reduced. In other words, because our closers are pitching fewer and fewer innings, their great strikeout rates and ERAs and WHIPs are less useful for a fantasy team.

But at least that’s happening to all closers, so the effect might be mitigated by the fact that we are all in this boat together. The second meaningful implication that modern bullpen usage has had on fantasy baseball does not impact all fantasy owners equally.

This might best be illustrated by example. Over at RotoWorld, I do a bullpen ranking article every week (Saves and Steals), and this year I’ve been forced to answer many a question about the placement of Jim Johnson in the “OK” tier. Why is a guy with this great of an ERA and WHIP so low on your rankings, kind sir, they ask politely. Because of the strikeouts, I say, while taking a sip of tea.

But maybe they don’t get it completely. As the average strikeout rate rises — especially the average strikeout rate of the top relievers, since the fantasy baseball universe is smaller than the baseball universe, and deals in top players — the replacement level for strikeouts from your closer rises. It’s pretty simple, really.

We’ll use K/9 to illustrate this even if K% is slightly better, and maybe you’ll see why shortly. The top 30 pitchers in saves last year had a 8.93 K/9 last season. That selection has a 10.1 K/9 this season. Jim Johnson has an 5.1 K/9 this season. If I have three average closers and you have three Jim Johnsons, and both relieving staffs pitched about 180 IP so far, my group would have 100 strikeouts more than yours by this point in the season.

Take a look at your standings — how many points higher would you be with 100 strikeouts? How about the 25-30 strikeouts if you have one Jim Johnson to my average closer? This will also be important very soon, when Wilton Lopez becomes a closer. He’ll be better than Co-Co Cordero, but he’ll only be a great fit on the right team (one with a ton of strikeouts elsewhere and a need for saves).

Jim Johnson is great. Jim Johnson is fine. But Jim Johnson also features a hidden cost to your season. And that has something to do with an extra roster spot, negotiated into the rule book some 25 years ago.