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What J.A. Happ brings to Minnesota

A fastball heavy approach that is evolving with age and modern pitching insights

American League Division Series Game 2: New York Yankees v. Tampa Bay Rays Photo by Alex Trautwig/MLB Photos via Getty Images

The first move of the Twins’ recent transaction spree was adding veteran left-handed starter J.A. Happ to solidify one of the open spots in the rotation. Now 38, Happ signed with Minnesota for 1 year and $8MM guaranteed and was announced by the team on January 22.

Since adding Happ the team has also added shortstop Andrelton Simmons and reportedly reached agreements with reliever Alex Colomé and designated hitter Nelson Cruz, in addition to making a small trade for right handed reliever Shaun Anderson and claiming right handed reliever Ian Hamilton off waivers.

It’s been a busy couple of weeks for the Twins and I’m a couple of weeks delayed in digging into Happ and what the Twins are getting with him in the rotation. You’ve probably read by now that he’s a solid back of the rotation starter who has leaned more heavily on his sinker as he’s aged and become more homer prone. You may also have seen that he benefited from an improved slider last season. While both of those things are true, the reasons behind them aren’t quite what they seem on the surface.


The lanky Happ (6’5, 205 lbs) debuted in 2007 with a single four-inning start for Philadelphia. He would add 8 more appearances (4 starts) and 31.2 innings for the Phillies in 2008 before finally breaking through to stick for good in 2009. Over the next 12 seasons, Happ would take the ball 315 times (293 starts) and cover more than 1,700 innings for Philadelphia, Houston, Toronto, Seattle, Pittsburgh, and the New York Yankees.

A third round draft choice out of Northwestern in 2004, Happ was not considered a top prospect and did not stand out as much more than a serviceable back of the rotation and depth piece early in his career. Through his first eight big league seasons Happ produced 7.6 fWAR while pitching to 4.24 ERA / 4.36 FIP over 840.2 innings.

Happ found significant success in his age 32 season after a mid-season trade to Pittsburgh and has maintained a higher level of performance in the 5 seasons since. Now, it’s clear that Happ is one of the rare “late-bloomers” who has been better in his 30s that he was in his 20s.

Starting with that 2015 season, Happ has pitched to 3.74 ERA / 4.08 FIP over 900.2 innings and accumulated 13.7 fWAR. Altogether he’s been 12% better than league average (88 ERA-). After the undistinguished start to his career, Happ has racked up the 22nd-most innings pitched, 32nd-most fWAR, and 45th-best ERA among the 173 qualified starting pitchers since 2015.

Last season, Happ appeared as strong as ever and rebounded nicely from a 2019 season that saw him struggle (4.91 ERA / 5.22 FIP). Crediting some mechanical tweaks that he said helped him feel more like he had in prior years, Happ had a 3.47 ERA / 4.57 FIP over 49.1 innings in 2020 while holding opponents to .208 / .273 / .382. Statcast largely backed up Happ’s success with it’s expected statistics derived from quality of contact data. Happ’s expected batting average (.222) and expected slugging percentage (.343) allowed tracked favorably with his actual marks. His 3.28 xERA, 26.3% sweet spot%, and 10.5% swinging strike rate were his best marks of the last six seasons and his barrel% (5.1%) and average exit velocity allowed (88.1 mph) were his lowest since 2017.

Despite his bounceback campaign, Happ and the Yankees had a tumultuous relationship and things were clearly headed towards a messy split after Happ indirectly accused the team of manipulating his usage early in the season to avoid a $17-million 2021 contract option. In the end, Happ fell one start and 10.2 innings shy of triggering that option, which the Yankees then declined, allowing him to become a free agent.

Arsenal & Approach

Thanks to a smooth delivery and positive fastball spin characteristics (above average spin rate, 90% active spin), Happ has found success with a fastball heavy approach. Despite below average velocity (21st percentile in 2020) that has slightly declined as he has reached his upper 30s, Happ has routinely thrown 65-70% fastballs throughout his career. He throws both a four seamer (44%, 91.6 mph) and a sinker (22%, 89.6 mph). In addition to the heat, Happ offers a slider (19%, 84.6 mph), changeup (14%, 86.4 mph), and infrequent curveball (1%, 80.9 mph).

Happ now deploys the four main offerings largely how you would expect. Four-seamers (red) up and to his glove side, sliders down and to his glove side (yellow), sinkers down and to his arm side (orange), and changeups down and to his arm side (green).

Last season, against right-handed batters, Happ relied primarily on his four-seamer (52%), changeup (19%), slider (16%), and sinker (11%). Against lefties, primarily his sinker (51%), slider (26%), and four-seamer (22%).

Leaning on the Heat

It’s the fastballs that have made things go for Happ. Among the group of 173 qualified starting pitchers since 2015 mentioned above, Happ’s fastballs rank 5th-best by pitch type linear weights. He’s in some pretty elite company by that measure:

Not only does he rank among the best in the raw accumulation (wFB), but he’s also 9th-best on a normalized, per 100 pitch basis (wFB/C). The totals in the table combine both four seamers and sinkers and Happ has generally gotten positive grades with both offerings, even as he has aged. Last season, he accumulated 7.5 wFB with them, and opponents hit .210 and slugged .452 against Happ’s four seamer and just .135 and .250, respectively, against the sinker.

While Happ has consistently leaned heavily on his fastballs throughout his career, he has increased his reliance on the sinker relative to the four-seamer steadily in recent seasons. His rate of sinkers and four-seamers last season were the 2nd-most sinker use and 2nd-least four seam use of his career — adjustments that are consistent with multi-year trends for both pitches.

That trend makes for a convenient narrative that he changed his approach as a way to address increasing home run troubles during his time with the Yankees. Homers were a big driver in Happ’s rough 2019 and his 1.9 HR/9 rate that season capped five straight seasons in which that number increased. Yankee Stadium’s small dimensions did him no favors and he allowed 34 home runs — easily the most he’s allowed in a season in his career. The fact that 25 of those long balls came off four seam fastballs adds some fuel to the thinking that more sinkers were Happ’s antidote to his home run issues.

But that simple story misses the fact that 28 of the 34 homers came against right-handed batters and Happ doesn’t throw that many sinkers to right handed batters. Despite the seemingly clear logic of more sinkers helping keep the ball in the yard, Happ’s sinker usage versus right-handed batters has not changed. In fact, it’s held steady around 11-12% of his pitches to right handers the past 3 seasons.

Happ’s increased rate of sinkers has come from dramatically increasing how often he’s thrown them against left-handed batters.

Back in 2015, only 2.7% of his pitches to lefties were sinkers (orange). Since, that fraction has increased steadily year over year and last season he threw sinkers more than half his pitches against lefties.

So the sinkers haven’t been in response to the home run troubles. Instead, they are part of multi-year evolution to improve the effectiveness of his whole arsenal through improved tunneling off his fastballs.

Evolving with experience (and modern pitching theory)

Happ has steadily evolved how he uses and locates his fastballs as he has aged. The location chart I showed you earlier hasn’t always been the case for him.

Matthew Trueblood pointed out at TwinsDaily shortly after news of Happ’s addition broke that no pitcher had more velocity and vertical movement differential between their four-seamer and sinker than Happ in 2020. That’s no accident, it’s by design.

In part to take full advantage of those characteristics, Happ has steadily increased the vertical location differential between his four-seamer and sinker the past six seasons. He’s done this by elevating the average location of his four-seamer:

Data sourced from

Interestingly, Happ’s four-seam elevation has come as his velocity has declined from 92.7 mph in 2015 to 91.6 mph last season. Similarly, his spin rate on the pitch — often a reason pitchers decide to work up in the zone more — has declined from the 82nd percentile in 2015 to the 55th percentile last season.

Counterintuitively, Happ’s response to an increasing propensity for giving up home runs with his declining four-seamer has been to throw it up even higher (something the Twins have been encouraging in recent years).

The gambit paid off for Happ’s four seamer last season, when batters produced .332 wOBA against the four-seamer (down from .367 in 2019) and the pitch allowed 88.1 mph average exit velocity, Happ’s lowest with the pitch in the Statcast era.

The multi-year adjustment has also benefited his sinker. Last season, opponents hit .135, slugged .250, and whiffed 21.8% of the time against Happ’s sinker — a far cry from 2015 when those numbers were .402 / .500 and just 12.8%.

Another part of the commonly reported story following Happ’s signing with the Twins was the improvement he’d experienced with his slider. Happ’s slider has been on again, off again throughout his career. He’s gotten negative weighted run values with the offering in seven of the past eleven seasons but two of the positive run value seasons have come in the last three years, including last season (1.0 w/SL). Opposing batters produced just .200 BA, .400 SLG, .244 wOBA and whiffed 31.7% against it last season.

Some have suggested some newfound movement created this success. While technically true, the Statcast data doesn’t bear this out in a very significant way. In terms of horizontal movement, the average break increased to 2.7 inches (up from 2.5 inches in 2019). Vertically, he increased the average break (including gravity) to 33.7 inches (up from 32.4 inches in 2019). An extra inch of downward movement is certainly helpful, but I would suggest the improvement with his slider has more to do with his increased sinker usage and the four-seamer location adjustment helping it play up.

Below is a 3D pitch tracking graphic of Happ’s arsenal against left-handed batters from Baseball Savant. The pitch colors are the same as we’ve been using — red for four-seamers, orange for sinkers, yellow for sliders. If you look (very) closely at what appears to be the beginning of the ball’s flight path, you can see three purple dots that mark the “commit point” for the hitter. This is the point at which a hitter must make a decision about what to do with the pitch. It is measured at 167 milliseconds (about 23 feet) before the ball reaches the plate.

Sourced from

Above, the purple marks are clustered pretty closely together, yet the three offerings end up in very different places, with different movement profiles, and different velocities when they reach home plate. For Happ against lefties, the sinker serves to pound them inside before going with the slower slider away or the faster four-seamer up and away. The four-seamer and slider tunnel together along the same trajectory, making them very difficult to distinguish from one another, especially when a hitter is worried about repeatedly getting jammed by the sinker moving in on their hands.

The same concept is true for right handed batters — but this time Happ includes his changeup (green):

Sourced from

Again, you can see the purple marks at the commit point are very tightly clustered. As the pitches approach home plate, they split. The four-seamer and slider track together and the sinker pairs similarly with the changeup.

Happ has the choice of pitches that deceive by tracking similarly or pitches that are opposite each other in location, velocity, and movement, as these PitchingNinja overlays show:

The upshot of all of this is, for hitters on both sides of the plate, Happ has multiple ways to attack them in different parts of the zone with pitches that look the same until it’s too late. Analyst Ethan Moore, now with the Twins as a research fellow, found Happ to be one of just 11 qualified pitchers with above average movement and tunneling metrics back in 2018.

This excellent pitch breakdown makes the complementary nature of Happ’s full arsenal clear:

What to Look For

Unlike other recent Twins pitching acquisitions, major adjustments don’t appear to be in store for Happ with Minnesota. He’s been a durable and consistent starter for a long time who has proven the ability to evolve and adjust. The Twins likely added him because of the stability he offers — not because he was a project they needed to work on.

That said, it’s almost guaranteed Happ will continue to tweak things with Wes Johnson and Josh Kalk. Under their leadership the Twins pitching staff has become baseball’s biggest users of breaking pitches, especially sliders. They love to help pitchers find ways to effectively tunnel their pitches. Johnson has a well known history of squeezing velocity out of pitchers through improved biomechanics. And, the Twins have a pretty good recent history with helping homer prone pitchers keep the ball in the yard (see Jake Odorizzi and Michael Pineda as two examples). Each of those areas seem ripe for further adjustment with Happ.

No, it’s not likely Happ will be more than a solid back of the rotation arm even with the Twins’ pitching voodoo on his side. After all, in FanGraphs’ write up of Happ’s signing they said the projection systems described him as the “fourthiest No. 4 starter who ever slotted into the fourth spot of a rotation.” But, that’s all the Twins need him to be and he is well equipped to meet those expectations.

John is a contributor to Twinkie Town with an emphasis on analytics. He is a lifelong Twins fan and former college pitcher. You can follow him on Twitter @JohnFoley_21.