Jeremy Jeffress blows bubbles as his shoulders heave with each breath. He stares at home plate like it threatened his mother. Both arms hang by his sides, almost making him appear defenseless. The way he clenches the ball in his glove reminds you that he is not. The bubble pops… he rocks purposefully and all the potential energy stored in his glare becomes a kinetic wave. His pitch hisses through the air as it spins and unwinds. The glove pops… 42,000 fans erupt as another door slams shut.

BREW MATHs dissects the pressure-filled moments JJ thrives on and strives to understand exactly how he does it.

CAREER STATS & TRENDS

INNINGS PITCHED: Jeffress has been utilized increasingly more as his career progresses

• Jeffress ranked 8th in games played amongst 2018 NL relievers

SABERMETRICS: All the most advanced pitching metrics show a downward trend. Regardless of which one you choose, they all paint the picture of a very good pitcher who is getting better. In 2018, most of his pitching stats were in the elite range.

• ERA-: Park adjusted ERA
• xFIP-: Expected Fielder-Independent Pitching (Park Adjusted)
• FIP-: Fielder-Independent Pitching (Park Adjusted)

RATE STATS: Rate Stats; Exactly what Brewers Fans want to see:

• Increasing strikeout rate (K%) with sharp rise over the last two years
• Declining walk rate (BB%) that has settled around league average

DEEPER STATS: Again, two powerful metrics that both tell a hopeful story:

• Batting Average On Balls In-Play (BABIP) – the overall quality of contact is decreasing as Jeffress’ evolves.
• Left On-Base Percentage (LOB%) – One of the most telling statistics for a reliever. If the point is to prevent runs and save the game, this is a good place to start.

• Last year, Jeffress led the league in LOB% with a rate of 92.9%!
• • If Jeffress inherited 100 runners, he would only let seven score, so how does he do it? Why the big improvements over the last two years?

LEFT: Opponents contact percentage has fallen sharply over the last several years.

• We see in 2018, it was well below league average (grey line)

RIGHT: A corresponding increase in Swinging Strike Percentage (SwStr%) validates that something is changing.

• JJ’s whiff rate over the last three seasons: 22.5 -> 23.8 -> 31.0

• Meatball percentage over same time: 5.4 -> 6.5 -> 9.0

interesting… while he is improving in terms of getting people to miss (a huge jump last year) he also is serving up more meatballs (aka easy for hitters to crush)

• Meatballs are typically right down the middle of the plate and can be any type of pitch. Major League Pitchers almost never try to throw right down the middle, so meatballs are synonymous with “mistake.”
• Since Jeffress’ overall stats are still improving, it implies that he is controlling the rest of the zone rather well…

Here is where things start to come into focus…

LEFT: Jeffress is getting guys to swing OUTSIDE of the zone, at a progressively higher rate over his career.

RIGHT: More importantly, when guys do swing at pitches OUTSIDE the zone they are missing them more. A lot more… And especially over the last two years.

Wow! In terms of manufacturing ground  balls, Jeffress has always been way above league average. In 2018, Jeffress was ranked 14th in the league in GB%, causing 56.4% of all contact to turn into grounders (pitchers with 50+ IP). Also of note, The Brewers recently signed Alex Claudio who had a GB% of 60.9 (good enough for eighth in the entire MLB!)

In order to figure out how Jeffress is getting such Brewer-friendly results, stratifying his pitch results is a great place to start:

• Over his career, Jeffress has used four pitches (Sinker, Fourseamer, Curve and Split)
  • Sinker: Opponents have hit this well, batting 0.283 with a BABIP of 0.306
  • Fourseamer: This has been hit even harder with opponents almost hitting 0.300 against it!
  • Notice how even though batting averages run high with certain pitches, the slugging percentages are still held in check.
  • • This tells us even when opponents are hitting Jeffress, they don’t typically go for extra bases.

• Jeffress’ ability to manufacture ground balls is impressive (look at the ground ball / fly ball ratio!)
  • Depending on which pitch he throws, the resulting ground ball rate is 2.5 to 7.55 higher than The fly ball rate!
• This distribution is consistent with a sinker / splitter pitcher that gets a lot of ‘topped balls’ to go for hard grounders (i.e. good double play balls)
  • Stearns has shown a predilection for ground ball pitchers and Jeffress is one of the best in the land.
• Of major importance, Jeffress uses four pitches very effectively.
  • Most MLB pitchers have 1-2 pitches they can consistently count on while Jeffress has four.
  • Early in his career, the fourseamer and curveball were exclusively used
  • In 2013, he began using the changeup and sinker more
  • Then in 2017, Jeffress started mixing in the splitter more
  • By 2018, Jeffress seemed to have perfected the balance and uses all four pitches relatively equally. The massive rise we saw in his K/9 and LOB% seemed to be a byproduct of this pitch selection.

PITCH REPERTOIRE

A very even distribution is seen between his pitches in 2018. We also see how he uses each of them in different areas. This forces hitters to guard against all of them all the time. Moreover, a sinker / splitter pitcher who uses a lot of two-seam movement relies heavily on the ground ball. This explains why his sinker and splitter are distributed lower in the zone.

If we look at how Jeffress has used pitches over time, we again see how the distribution evens out. Specifically, since 2016 (when Jeffress began rapidly improving) we can see how all four of his main pitches begin approaching a single point. The pie chart below really stresses this equal distribution:

Pitch Repertoire Summary

• Over his career, Jeffress’ armory expanded from a two-pitch approach to an evenly distributed four-pitch attack
  • The addition (and perfection) of these pitches has allowed him to be more than a power pitcher
  • Keeping hitters off-balance is now easier for JJ that he is comfortable with four pitches
  • • The sharp rise we see in his stats over the last three years has more to do with pitch selection and control than velocity
  • • As he has gotten better, every pitch has become more effective. Jeffress is not just leaning on one trick. He now has a whole bag.

This chart is beautiful because Jeffress ‘paints’ with all four colors (pitches) equally. Some trends jump out:

• Jeffress rarely throws the split finger early in the count
  • A hitter is progressively more likely to see it as the count wears on
• When he is behind in the count, JJ is much more likely to throw fastballs
  • However, he clearly is confident with all four pitches since they are evenly utilized when facing a full count.
• When he has a hitter backed into a corner (2 strikes), they have to guard against everything.
  • Jeffress utilizes a lot of ‘two-seam’ movement to get the elite GB% we have already discussed.
• The knuckle-curve is never used on a 3-0 count
  • This reinforces the idea that Jeffress welcomes contact at times
  • He still attacks the strike zone when behind in the count and relies on ground ball outs to get him out of trouble.

VELOCITY

In terms of durability, we do not see a fall off in his velocity. There has been a small down-trend in his fastball velocity while his curve has sped up 8-10mph since his rookie year. In the end, the raw speed is not as important as the distribution of the speed:

JJ has four pitches, three of which come in at markedly different speeds. His curve averages right around 80mph, while his fourseamer and sinker fall between 95 & 100mph. His splitter is elite and averaged 90.6mph last year, good enough for second fastest in the entire MLB:

Hitters are in a continual state of unrest having to guard against four different pitches, each of which is released from the same spot. Jeffress’ ‘blow it by you’ approach has evolved to include surgical precision. This allows JJ to maximize deception while limiting reaction times.

RELEASE POINT

Consistent with fooling hitters, we see how all of these pitches end up looking fairly similar to a hitter. The knuckle-curve is thrown a bit more laterally to generate the necessary spin. However, all three of the other pitches come from the same spot. What makes it so difficult for opponents is that all three move differently and come in at different velocities.

OVERALL ACCURACY / PLACEMENT

The mid to lower part of the zone is pounded with all four pitches and in a fairly equal distribution. He prefers his sinker to drop with a glove-sided movement, while the splitter has more of an arm-sided diving motion. These pitches look the same until it is often too late. Hence, all the strikeouts and ground balls.

This 2018 zone chart helps us to understand how Jeffress can simultaneously have a high whiff rate AND a high meatball percentage. He clearly can work the edges and finds that vast majority of pitches end up there (note the strike zone demarcated with dotted line). However, he also ends up missing down the middle a significant portion of the time (i.e. meatballs). The reason for this will be evident once we review the video under ‘pitch-by-pitch execution.’ Before that, let’s consider a few different iterations of heat map.

• The heat burns the brightest in the lower, glove-side corner
• While he is good at working the lower edges, it is easier to see here how many of his pitches slip further into the zone.

LEFT: When JJ is AHEAD in the count, he tends to work more centrally. He is a pitcher that thrives on working the edges but keeps the count balanced with good zone command. The pitches are not as surprising to see clustered in the strike zone being behind… he is in ‘battle back’ mode.

Jeffress uses velocity and location to maximize his effectiveness. That said, he is below average in terms of motion with his pitches. Thus, if misses a pitch up in the zone they tend to be barrel magnets (i.e. meatballs)

RIGHT: When he is BEHIND in the count, he looks for the edges more. His two-seam approach really shines through in this heat map. The sinker and split finger both have the ‘drop off’ effect, making them well suited for low in the zone. Even if he misses and hard contact results, it typically leads to a grounder as long as it is low.

PITCH-BY-PITCH EXECUTION

All zone charts in this section show where Jeffress got his strikeouts with the respective pitch (colored dots)

• Primary Pitch; thrown with a Knuckle Curve Grip
• Averages about 82mph
• Generates whiff rates much higher than the average MLB curveball primarily due to his ability to locate it (86 percentile)
  • Surprisingly, this pitch has a low amount of vertical break (37th percentile) and late break (39th percentile)
  • Thus, how effective it is has less to do with movement and more to do with  velocity / location.
  • This makes it more understandable how JJ can have BOTH a high whiff and a high meatball rate.

When the KC goes where JJ wants it to:

When the KC is left up in the zone (i.e. meatball):

• Secondary Pitch; Very fast with armside run
  • Averages 96mph! (98th percentile)
• Generates very high whiff rates (consistently near the league lead)
  • Location (82nd percentile) and rise (71st percentile) are the primary reasons this pitch is successful
• Where the curve’s efficacy lies in its placement and control, JJ’s sinker is one of the nastiest in the league. So fast!
• NOTE: In the video, BA calls the pitch a splitter but it behaves more like a sinker
  • The two-seam spin that Jeffress uses with the majority of his pitches even makes it hard for the announcer to pick them up. Imagine how hard it is for hitters!

• Third most used pitch; The equalizer (the power of this pitch potentates the effect of his two-seam approach)
  • Exceptional velocity (96mph; 85th percentile) with lower than average movement (little horizontal motion with almost no late break)
  • Above average rise (67th percentile) and vertical break (60th percentile)
  • JJ is very good at locating this pitches
  • 82 overall quality of pitch (QOP/QOPA)
• While opponents hit this pitch hard, it usually stays in the park
  • Jeffress has only given up 30 HRs in his career and at a clip of 4.72 HR/FB with this pitch
  • Moreover, it is a real worm killer (he generates ground balls at a much higher rate than league average (JJ gets 2.6 times more ground balls than fly balls with this pitch; his other pitches are even better in this regard!)

When the fourseamer is used effectively (late in sequence on edges; most effective up in the zone):

When the fourseamer gets too much of the plate (rare):

• Least utilized of his main pitches; that said, he throws it regardless of the count
• One of the best ground ball generating pitches on the planet
  • Averages 91mph (98th percentile) with immaculate placement (82nd percentile)
  • This pitch looks very much like his other fastballs but offers a different trajectory. We see Harrison’s bat in the entirely wrong plane when he takes this swing, the splitter gets him:

QUALITY OF PITCH

• Jeffress throws high-caliber pitches across the board (4.89 QOPA / 86th percentile overall).
  • JJ’s strengths, ranked: 1) Horizontal break 2) Location 3) Velocity
• The elite velocity his fastballs possess set up the sweeping knuckle curve nicely
• Jeffress technically gets ‘hit hard’ but many of them are topped (2 seam action pulls ball down). Hence, the high GB%.

THE RESULTS

By expanding and balancing his approach, Jeremy Jeffress has learned to keep hitter’s off-balance. We see a decrease in overall pitch effectiveness around 2013. This is when Jeffress starts to retool his approach and added two more pitches to his regular repertoire. Then in 2017, he learned how to use the splitter in concert with the other three pitches. This maximized his effectiveness as batter’s now had to be ready for anything. The rapid improvement in his stats over the last two years suggest JJ is approaching the peak of this game. As of 2018, every pitch but his splitter has a rising whiff rate (above). The All-Star is honing his craft!

This is where we see the power of Jeffress approach. He generates grounders so reliably that it allows him to own the strike zone. Even when he is inviting solid contact, it is being driven straight into the ground. Therefore, take his above average hard hit % with a grain of salt. The scatter plot and map tell you everything you need to know about where the hard hit balls go (i.e. down).

LOOKING AHEAD

This is where things get scary for opponents… Jeffress isn’t just getting better at placing his pitches and balancing his repertoire… he is also learning to get them to dance more!

• His curveball has five inches more vertical break than it did when he started… five inches!

QUICK LOOK: COMPARED TO RIVERA…

If we use an age plot and compare Jeffress to the ‘greatest reliever of all time’ the results are pretty encouraging. At the same point in his career, Jeffress is now better than Rivera in every one of the metrics represented below (FIP, WHIP, K/9 and LOB%)! We see what made Rivera great is his consistency over the last 15 years of his career… JJ seems to be on the same path.

INTERPRETATIONS / CONCLUSIONs

• Jeremy Jeffress uses a high velocity, two seam approach. His pitches look the same, limit reaction time and move differently
  • He has learned how to expand his repertoire and sequence his four pitches in a way that never lets hitter’s get comfortable
  • JJ generates one of the highest ground ball rates in the entire MLB (14th last year)
  • His rising meatball rate is likely the byproduct of him learning to implement a larger repertoire. Growing pains, so to speak.
• As his career has progressed, he has improved by almost any advanced metric you measure him by
  • Most predictive of things to come, his rate stats (K% / BB%) have steadily trended in reassuring directions. The man is definitely getting better and honing his craft. A power pitcher who is mastering the cerebral game and sharpening his control.
• If Jeffress simply continues on the path he has been on, he will be remembered as one of the greatest relievers ever. His moustache may start to curl…