Best 2019 MLB Bullpens – Strikeout Artists

The bullpen. The late-inning firefighters who deliver those last outs and secure precious victories.

Good bullpens bridge the gap between a .500 season and a world championship. The Cubs signed Craig Kimbrel, for example, in the hope that their bullpen is now World Series-ready.

Take a look at the Bovada World Series futures odds. All of the teams at the top have shutdown bullpens. It is extremely important to be solid on the back end in the postseason.

So which teams can be trusted to hold a lead? Who are the best bullpens in the MLB?

I wanted to focus on one specific area of bullpen effectiveness today – strikeouts. I will explore which bullpens strike out the most hitters, which throw the hardest, which miss the most bats, and which need to start throwing more strikes.

Strikeouts Per Nine Innings – K/9

In the final three innings, when adrenaline is pumping and nerves are at their highest, being able to strike out hitters becomes invaluable. Strikeouts eliminate the need for fielders to take a good route, make a clean transfer, and throw the ball across the diamond.

Teams often load their back end with flamethrowers who specialize in getting Ks for this very reason. Here are the top-5 bullpens of 2019 ranked by strikeouts per nine innings (K/9).

The Red Sox are crushing the rest of the league in bullpen strikeouts, recording over half a strikeout more per 9 innings than the second-place Yankees.

The Sox top-three strikeout leaders from the pen, Matt Barnes, Brandon Workman, and Marcus Walden, are leading the charge.

Each of these men have been tasked with doing the heavy lifting in the Boston bullpen. The trio has combined for 115.3 innings this season – tied for the 9th most innings by a trio in the MLB.

What few other trios can match are the strikeout capabilities and the ability to limit both hits and runs that these 3 pitchers possess.

Matt Barnes’ 15.99 K/9 rate seems high … and it is. Among all MLB relievers, Matt Barnes averages the 2nd-highest strikeouts per 9 innings, behind only Josh Hader.

Brandon Workman’s elevated BB/9 rate is scary until you realize that he is striking out nearly 13 batters per 9 while holding hitters below a .100 batting average. He is getting the job done.

Marcus Walden’s contributions this year have largely been hidden by the first two talents on this list, but he is having an All-Star-caliber season.

Tigers’ reliever Joe Jimenez made the All-Star team in 2018, posting a 1st-half line of a 2.72 ERA, .216 opponent average, and 10.05 K/9. Walden’s numbers match if not exceed Jimenez’s.

The Fastest Throwing Bullpens

The pitchers who rack up the most strikeouts must be able to blow it past Major League hitters. Throwing hard is not the only ingredient to good pitching, but flamethrowers have a greater margin for error. Fast throwers are typically better late-inning bullpen pitchers than their soft-throwing counterparts.

Fangraphs has pitch velocity data for each pitcher, allowing us to easily see which bullpens light up the radar guns.

The following chart shows the top-5 bullpens ranked by average fastball velocity.

I’ll say it again – throwing hard is not everything, not even close. Despite their abundance of mitt-popping talent, Miami’s bullpen ERA in 2019 is 5.12. Only 3 teams in baseball are worse.

Throwing hard does not even guarantee strikeouts, either. The White Sox are tied for the hardest throwing pen in the Bigs and yet rank 27th in bullpen Ks.

Other bullpens on this list, like Houston and Cincinnati, are having tremendous seasons. So what gives? Why are some hard-throwing pens dominating and others suffer meltdown after meltdown?

The key is not how hard these pitches are coming in, but where they are located.

Z-Swing% and Z-Contact% 2019 Bullpen Leaders

Junk ballers will often try to get hitters chasing out of the zone. Flamethrowers normally come right after guys – challenging them with cheese in the strike zone.

Even if you throw 105 MPH, you still need to locate your pitches on the inner or outer third of the plate. Pitches right down the middle, regardless of the speed, get hit a long way in the MLB.

There are two plate discipline stats which effectively quantify which pitchers are the best at missing bats on pitches inside the strike zone – Z-Swing% and Z-Contact%.

Z-Swing% is simply the percentage of pitches inside the strike zone that the batter swings at. Z-Contact% is the percentage of those swings in which the batter puts the ball into play.

Pitchers with low Z-Swing rates are adept at putting pitches right on the corner and freezing hitters. This can be an effective way to strike hitters out. Pitchers with high Z-Swing rates but low Z-Contact rates are the guys with untouchable, swing-and-miss stuff. This is also an effective way to rack up Ks.

Here are the top-5 and bottom-5 bullpens in Z-Swing%. I also included each team’s rank in bullpen K/9 so we can see which method has worked best in 2019.

The bullpens at the bottom of the league in Z-Swing% are the same ones populating the top of the bullpen K/9 leaderboard.

A high Z-Swing% is not bad as long as the opponents Z-Contact% is not too high. Here are the top-5 bullpens of 2019 in Z-Contact% against, also with their ranks in K/9.

The bullpens with low Z-Swing% against rates were killing it in strikeouts. These pens with low Z-Contact% against rates are also near the top of the league in Ks.

It goes without saying that if a bullpen can catch hitters looking and get them to swing through pitches, they will be tough to hit.

This data is strictly for pitches inside the strike zone. We have not yet talked about pitches outside of the zone, which can be equally important.

O-Swing% and O-Contact% 2019 Bullpen Leaders

I have talked about O-Swing% and O-Contact% several times in the past and will reference them again here. I will also incorporate F-Strike% (1st-pitch strike %) as getting ahead in the count is of paramount importance to relievers who typically have fewer pitches in their arsenals than starters.

Getting that first-pitch strike and commanding the at-bat will force the hitter to protect the plate and chase pitches he otherwise would not offer at. First-pitch strikes are the recipe for success.

Before I show a graphic of several pens’ numbers in these areas, I want to provide the league averages for context. The following chart shows the average O-Swing% against, O-Contact% against, and F-Strike% for all relief pitchers in 2019.

O-Swing% against	30.9%
O-Contact% against	60.8%
1st Strike%	59.7%

With that context in mind, take a look at this next graphic. I took the top-10 bullpens in strikeouts per nine innings and listed their O-Swing, O-Contact, and first-pitch strike numbers.

Surprisingly, only 4 of the top-10 bullpens in K/9 have a first-pitch strike rate above the league average.

Boston’s is a tad low, but they catch a lot of hitters looking to make up for it. The Sox’ O-Swing% against is also quite low, meaning that they cause plenty of hitters to chase also.

There may be an opportunity for value here as Boston’s bullpen seems to be playing with fire. Historically, first-pitch strikes are the key to successful pitching. Pitchers who consistently fall behind in the count do not hack it for long in the MLB.

Does Boston have a good bullpen filled with talented arms? Yes. Is the Sox pen talented enough to average 10.76 K/9 throughout the entire season? Probably not.

I will take a few chances on some overs or prop bets against the Red Sox bullpen over the next couple of weeks. All it takes is one or two extra hits to blow a lead and ruin a game.

Once opposing hitters figure out that they can afford to be a little more patient against Boston’s relievers, they will begin to be served some more hittable pitches.

I am not predicting an epic collapse. I am simply saying that Boston’s bullpen performance through the first 3 months of the season is unsustainable. The Sox are due for a regression back to the mean.

Happy 4th, boppers! See you on top!