Here’s a stat about strikeouts: The percentage of 50-plus-inning relievers who struck out a batter per inning in 1990 was lower than the percentage who struck out 12 per nine innings in 2012. Remember the Reds’ “Nasty Boys” bullpen of Rob Dibble, Randy Myers, and Norm Charlton? They were three of only eight relievers with a K/9 of at least 9.0 in 1990. Relative to average, Dibble’s 12.5 K/9 that season was more impressive than, say, Aroldis Chapman’s league-leading 15.1 in 2013. But 15.1 is such an astounding number that it commands the attention anyway. Strikeout rates are rising too fast for the baselines in our brains to keep up.

Every season, a new crop of relievers arrives and astonishes us with their strikeout prowess. Some are promising rookie relief prospects who throw a million miles per hour and were expected to miss many bats. Others are rookies who’ve exceeded expectations, and still others are veterans whose latent strikeout powers were never suspected before they surfaced this season.

The following 10 pitchers have thrown at least 10 innings in relief and struck out (approximately) everyone, without any prior insane strikeout rate seasons.* There are other eye-popping relief lines that come with more modest strikeout rates, but those won’t appear in this article. As wonderful as it is that soft-tossing 26-year-old Twins rookie Caleb Thielbar, whom we discussed on Effectively Wild last week, has started his career with 16 2/3 scoreless innings, he’s also struck out under eight batters per nine innings, walked almost four, and given up a lot of fly balls. You can enjoy the fact that none of his batted balls has been a homer and that very few of his batted balls have been hits, but not without a sense of impending doom that sort of spoils the small-sample success. The higher the strikeout rate, the lower the flash-in-the-pan potential, so some of these guys might have a slightly longer life expectancy than the typical non-Rivera reliever.

1. Shawn Kelley, Yankees (13.1 K/9, 31.0 IP)

Strikeout pitch: Slider (44.3 percent whiff/swing rate)

Strikeout pitch video:

Strikeout rate origin story: The same as that of almost every hero, from Jesus to John Frusciante: face some sort of trial, survive it, and come back stronger than before.

Kelley had his second Tommy John surgery in 2010, and by the time he returned, he realized that he had to change his approach. In 2009, he’d thrown 59.0 percent of his pitches inside the strike zone, the second-highest rate among pitchers who threw at least 400 pitches that season (behind Paul Byrd). Like Byrd, he didn’t walk anyone, but his strikeout rate wasn’t anything special. Last year, he threw 53.3 percent in the zone and had some success, but he still had trouble finishing hitters off. So he’s cut back to 49.3 percent this season, and that seems to have helped. Kelley’s fastball is average, but if he keeps it down, it works well with his nasty slider.

The Star-Ledger’s Andy McCullough offers more details on Kelley’s evolution here. It’s clear that Kelley’s strikeout rate has surprised not only the man who hired him

“The strikeouts per nine,” Cashman chuckled, “are higher than what we traded for.”

But also his catcher

“It’s a question we’re trying to figure out down in the bullpen all the time,” catcher Chris Stewart said.

And Kelley himself

“After the game I’ll be like ‘Man, I never strike guys out like that,’” Kelley said. “Striking out the side? I never strike out the side.”

Since that story was published, Kelley has struck out seven in 7 2/3 innings, so this could be a Strikeouts for Algernon situation.

2. Danny Farquhar, Mariners (13.0 K/9, 19 1/3 IP)

Strikeout pitch: He gets more whiffs with his four-seam and curve, but the cutter is the key to his newfound success.

Cutter video:

Strikeout rate origin story: Complete mid-career reinvention.

As chronicled here, Farquhar has changed almost everything about himself since a 2011 cup of coffee with Toronto, when he looked indistinguishable from any number of forgettable righty relievers. At the time he threw sidearm sinkers and sliders, like so,

and his four-seamer sat in the low 90s. Now he throws from a ¾ angle and uses a cutter almost half of the time, and his 86 four-seamers have averaged almost 95 miles per hour.

Farquhar bounced between four organizations last season, joining the Mariners at the minor-league level after his inclusion in the Ichiro trade. His K rate ticked up in Tacoma early this season, and the Mariners gave him a shot. He’s been up ever since, though he’s appeared mostly in low-leverage outings and hasn’t pitched since June 23. A 6.05 ERA has something to do with that, but he has the peripherals (and, surprisingly, the stuff) of a useful arm against hitters of either handedness.

3. Robert Coello, Angels (12.9 K/9, 14 2/3 IP)

Strikeout pitch: The WTF (30.8 percent whiff/swing rate)

Strikeout pitch video:

And a closer look, courtesy of SB Nation:

Strikeout rate origin story: A unique pitch combined with a conversion from catcher.

Much has been written about Coello’s signature offering, which shares some characteristics of a forkball, knuckleball, or splitter, but isn’t any of those things. “The WTF” is what Coello calls it, and it defies classification. Whatever it is, hitters can’t hit it, and catchers occasionally can’t catch it.

Coello has been able to throw the WTF since high school, but he was drafted in 2004 as a catcher and didn’t start pitching until 2007, his first season with the Angels (in during his first tour of duty with the team). Injuries and control problems prevented him from establishing himself at the big-league level until the Angels were in dire need of relief help earlier this year, at which point GIFs of the WTF made him a household name among the small subset of fans who consume baseball via endlessly looping animated images. Unfortunately, elbow and shoulder soreness ended his strikeout run. He’ll be shut down until the middle of this month.

4. Alex Torres, Rays (12.1 K/9, 23.0 IP)

Strikeout pitch: Changeup (43.3 percent whiff/swing rate)

Strikeout pitch video:

Strikeout rate origin story: Mechanical tweaks.

Through last July 30, Torres—a product of the 2009 Scott Kazmir trade—had walked 61 batters in 61 2/3 innings at Triple-A Durham. As Tommy Rancel writes here, the Rays sent him all the way down to the Gulf Coast League, where he worked with pitching coach Marty DeMerritt, who’d known him since he was a teenager. DeMerritt helped him smooth out his mechanics and reposition himself on the rubber, and his control improved.

Torres’ stuff was never in question, and now that he can throw strikes, the overall package is impressive. The lefty’s four-seamer has averaged almost 93 miles per hour, and he has a highly effective changeup that he’s not afraid to throw to same-sided hitters. He’s made himself into a late-inning option, and he’s also made an impression on opponents: last month, Jim Leyland said he “looked like Warren Spahn, Sandy Koufax, and Whitey Ford all put together.” The balls have all bounced his way thus far, but he doesn’t look like a mirage.

5. Kevin Siegrist, Cardinals (11.7 K/9, 10.0 IP)

Strikeout pitch: Four-seam fastball (31.3 percent whiff/swing rate)

Strikeout pitch video:

Strikeout rate origin story: Is on the Cardinals. Okay, and a bullpen conversion. And velocity and deception.

Siegrist was drafted in 2008 in the 41st round, which is not one of the early ones. Working mostly as a starter from 2008-12, he struck out 222 and walked 111 in 284 2/3 innings (7.0 K/9). He posted low ERAs, but didn’t have the stuff to succeed as a starter; in a May 2011 Minor League Update, Kevin Goldstein wrote, “scouts see a smoke-and-mirrors lefty who rarely gets out of the 80s with his fastball.”

That’s not who scouts see now. This season, following a successful stint in the Arizona Fall League, Siegrist was moved to the bullpen full time. The new role agreed with him: in a combined 27 2/3 innings across Double- and Triple-A, he struck out 44 and walked 10 and was named the Cardinals’ Pitcher of the Month in May.

On June 6, Siegrist became the eighth rookie pitcher to debut for St. Louis this season, and he hasn’t allowed a run yet. He throws a four-seamer and sinker around 95 mph—no smoke or mirrors needed—supplementing the hard stuff with a curve and an occasional changeup. And remember, he’s a lefty. It’s good to be a Cardinals fan.

Not only does Siegrist throw hard, but he throws across his body and hides the ball well, which—according to Tim McCarver, who raved about him in a recent Fox broadcast—is unusual for someone so tall (Siegrist is 6’5”.) That deception makes the velo play up more, leading to a lot of weak swings.

The one thing Siegrist might not be is an interesting quote. About his success this season, he said, “I’ve just been consistent with my fastball, not walking a lot of guys. Trying to keep that up.”

6. Carter Capps, Mariners (11.4 K/9, 31 2/3 IP)

Strikeout pitch: Slider (54.2 percent whiff/swing rate)

Strikeout pitch video:

Strikeout rate origin story: It’s boring, but…natural talent.

The Mariners’ system is strong, so Capps didn’t quite crack this season’s Seattle top 10 list, but an upper-90s fastball that Jason Parks noted “can kill a man” qualified him for “Factors on the Arm.” The righty was expected to “emerge as a late-inning force in the years to come,” thanks both to his heater and a refined slider that I profiled in April.

It hasn’t happened this year. The strikeouts are there, but Capps has allowed nine home runs in 31 1/3 innings, and he’s been destroyed by lefties (.340/.404/.766). As a low-arm-angle righty who relies on a slider, Capps will always be vulnerable to southpaws, but he should be an effective situational option when he lives outside the zone a little more and gets over the gopheritis (which has never plagued him in the past).

7. Manny Parra, Reds (11.4 K/9, 19.0 IP)

Strikeout pitch: Splitter (77.8 percent whiff/swing rate)

Strikeout pitch video:

Strikeout rate origin story: Bullpen conversion, new pitch, and improved breaking stuff.

Parra had an 8.10 ERA in April, then spent 30 days on the DL with a pectoral strain. Since his return, he’s allowed four runs in 16 games and 12 1/3 innings, striking out 17 against four walks. Parra throws a little harder out of the pen than he did as a starter, and according to Brooks Baseball, he’s added a slider (at the expense of his four-seamer), which he threw as a prospect but then went away from and which has gotten him plenty of grounders and whiffs.

Even out of the pen, Parra has never before had a season with a walk rate under four per nine, so his current rate (3.3/9) represents real progress. But the extra strikes are all coming outside of the strike zone: Parra’s zone rate is unchanged, but he’s getting more chases. He recently cited improved breaking stuff—and a willingness to throw it even when behind in the count—as the reason for his success, and his story checks out.

With Sean Marshall injured, Parra has taken on a more prominent role in Cincinnati’s bullpen. On the glass-half-empty side, the slider has done nothing to reduce his platoon splits, so he could be headed for a LOOGY role.

8. Cody Allen, Indians (10.7 K/9, 33 2/3 IP)

Strikeout pitch: Curveball (52.9 percent whiff/swing rate)

Strikeout pitch video:

Strikeout rate origin story: Filth.

Allen has never not struck people out. The 2011 23rd-round draftee—not a Siegrist late selection, but late enough that it’s a surprise to get someone useful—whiffed almost 12 per nine innings without many walks in the minors, and he has the kind of stuff that eventually makes its way into save situations. His fastball averages almost 96 mph, and only Craig Stammen, David Robertson, and Tony Cingrani have higher curveball whiff rates.

9. Will Harris, Diamondbacks (10.6 K/9, 18 2/3 IP)

Strikeout pitch: Curveball (31.3 percent whiff/swing rate)

Strikeout pitch video:

Strikeout rate origin story: Going to go with "deception."

Harris, who switched teams twice on waiver claims in April, isn’t overpowering, but Kevin Towers has a knack for finding unwanted arms who can help his clubs. The righty’s cutter velo is up since last season, but still sitting in the 92-93 range. He throws a curve, but it’s not a big bat-misser, and he doesn’t get a lot of swings outside the strike zone. He has gotten ground balls this season, he hides the ball well, and he has struck out almost 12 batters per nine in the minors, though that seems to have surprised all involved. He’s like a bigger, but not better, version of Allen. Oh, and he’s 28. Adjust your expectations accordingly.

10. Brett Cecil, Blue Jays (10.5 K/9, 43.0 IP)

Strikeout pitch: Curveball (50.6 percent whiff/swing rate)

Strikeout pitch video:

Strikeout rate origin story: Bullpen conversion, mechanical/pitch selection tweaks.

Cecil was a below-average starter, and like a long line of below-average starters before him, his path led to the bullpen. Now that he’s working in short bursts, his four-seamer has added a few miles per hour, and he’s abandoned his slider. He's also altered his delivery. The result has been many more whiffs. The southpaw has the fourth-lowest BABIP among pitchers who’ve thrown at least 40 innings, and his HR/FB rate is out of whack, too, so there’s some sort of correction coming. But becoming a full-time reliever has been a great career move.

(And if you’re wondering where Neal Cotts is, he got his own article.)

*If you want to read about some repeat insane strikeout seasons, Doug Thorburn has you covered.

Thank you for reading

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Hi Ben,

Enjoyed the article. You must have put in a tremendous amount of work. How much of the high strikeout rates are due to changes in hitting style? For better or worse, the stigma of striking out has decreased over the past 20 years or so. The hitters today are hacking with two strikes. I am not saying it is a bad thing, but that may explain some of the rise in strike out rates.
Re Cody Allen, David Robertson, and Craig Stammen -- all of them use the "spike" grip on their curve.
One of the biggest changes for Cecil is that he spent the offseason following a weighted-ball training routine that his teammate and fellow out-of-nowhere strikeout extraordinaire Steve Delabar brought into the spotlight. It greatly strengthened his shoulder and has added a ton of zip to the fastball/sinker. One of the founders of the program has since been hired by the Blue Jays organization.

The curveball is just a thing of beauty though.
Good information.
Now I feel the urge to go back and watch all their innings on MLB.TV

Did you mean full time reliever with Cecil?