Pitching by the Numbers: Special K relievers

We have enough of a sample now to look at relievers given that it takes only about 70 at bats for a pitcher’s K-rate to stabilize. The stat we’re interested in with them is primarily saves but also their ability to generate surplus Ks. My formula is keeping their K-rate at a solid 9.0 per nine innings (a winning number in innings-capped leagues) and giving the surplus Ks from that reliever to the rest of your staff.

Each surplus strikeout actually raises the K/9 rate of other pitchers by a full K/9 for, of course, nine innings. So when we look at the top surplus strikeout pitcher on our list, the Yankees’ Dellin Betances, we get a better sense of his true impact on a staff with this calculation. His 41 Ks in 26 innings for a surplus of 15 Ks will raise the K/9 of the rest of the staff by 1.0 for 135 innings (15 times 9).

Let’s look at the other leaders among relievers in surplus Ks, through Wednesday’s action.

Basically now we have a closer ranking that includes this surplus strikeout statistic: Chapman, Miller, Robertson, Allen, Kimbrel, Tolleson, Grilli, Storen…..

Right now, you’re thinking I’m crazy ranking Allen so high given his 6.34 ERA. But we hardly care about ERA over 19 innings. We do care about those 28 Ks. The tricky thing, of course, is that the managers care about the ERA and the blown saves it creates. We can’t ignore that. But if you could guarantee me that the Indians would keep throwing Allen out there, I’d expect his ERA going forward to reflect that K rate and thus be good. I am troubled by this walk rate, but that takes more than twice as long to stabilize and we’re not there yet. See this helpful list from Fangraphs for more on stabilization rates.

Jason Grilli is similar. He’s given up way too many hits given all those Ks — his BABIP is .359 (Allen’s is .396). You show me 23 Ks in 16.1 innings for a closer and I’m rostering him every time. In fact, I have Grilli, Betances and Robertson on my Friends and Family team and they are effectively raising the K/9 of my staff by a full 1.0 for 278 innings. Of course, Betances’s averages are great, too, but he’s not the closer and unlikely to be barring an injury to Miller. Still, he should be rostered in every format.

You could say the same thing about other non-closers Garcia and Burgos. Unfortunately, Burgos is now on the DL with shoulder woes.

Is Boxberger a closer? He should be given his dominance (28 Ks and 8 BBs in 18.3 IP). But he’s taken the loss in consecutive days and Jake McGee lurks. Still, he’s valuable because he’ll pitch more and get more Ks if he loses his job.

What about closers the other way, the ones who are actually hurting you strikeout numbers? Here’s the full list - focus on the bottom.

Tyler Clippard, Luke Gregerson, Glen Perkins and Fernando Rodney are below the threshold but not egregiously so. This shows you how important K rate is to being a closer and helps us when speculating on future saves. If the guy isn’t posting a rate of at least a K per inning, you should speculate elsewhere.

A surprise non-elite strikeout reliever (who has closed this year) is Wade Davis. His stuff seems to have taken a step back in 2015.

Conversely, we can speculate on possible future closers where the current one is not firmly entrenched either due to age, recent history or possible trade. We’ve already highlighted Burgos, who, again, is disabled. But Fields seems like he should be closing right now and was not that long ago a first-round pick for the purpose of doing just that. Tolleson has already rewarded our faith based on this stat. I don’t know what to make of R.J. Alvarez, but he’s back in the minors. Harris is another closer candidate in Houston, which has a solid ‘pen. Although Gregerson has a 3.92 ERA, his save percentage and WHIP are good and his K rate is good enough.

Given that the Brewers are a terrible team and could trade 33-year-old Francisco Rodriguez, now throwing below 90 mph, I think Smith should be rostered immediately. While he’s a lefty, the 34 righties he’s faced are hitting .100 off of him and he’s among the league leaders in swinging strike rate. He also throws hard enough — about 93 mph.