Flying Heim: Is Jonah’s Heim Breakout for Real?

Is Heim a top-five catcher in the game?

Jonah Heim has emerged this season as both a great player and a valuable catcher for fantasy baseball teams.

He exploded out of the gates with five home runs and 22 RBI in 23 games in March and April before slowing a bit thus far in May. As of May 23, he still has an overall slash line of .288/.348/.473 for the season, which is among the top in the game for catchers. He has a total of six home runs and his 32 RBI are the second-most by a catcher.

Heim has been a major catalyst for a Rangers offence that is firing on all cylinders and is leading all of baseball in team batting average (.271), total runs (307), and RBI (295). He’s also a major reason why the Rangers are exceeding expectations and sit in first place in the AL West with a 29-18 record (as of May 23). Before the season, ESPN gave the Rangers only a 37% chance of making the playoffs and predicted an 83-79 record, while CBS predicted a fourth-place finish in the division.

So this begs the obvious question: is Heim’s breakout season sustainable or is the hot start imply a mirage in the dry Texas heat?

Let’s review Heim’s career to see how he got to where he is today and the changes he’s implemented that have led to his success this season.

A Minor(s) Detour


The 27-year-old Heim is a New York native who has had a winding journey of a career before finding success this season. He was committed to playing baseball for Michigan State but then was drafted by the Baltimore Orioles in the fourth round (129th overall pick) in the 2013 MLB Draft.

During the 2013 season, he played 27 games with the Orioles rookie level team he hit .185/.275/.247. Over the next few years, he climbed to Single-A in the Orioles farm system before being traded to the Tampa Bay Rays in August 2016. He played a total of 102 games that season, hitting .217 with eight home runs and 33 RBI.

Heim had his best season yet in 2017, as he played 93 games across Single-A and High-A in the Rays system, hitting nine home runs and 61 RBI with a .260 batting average. However, after the 2017 season, he was on the move again, as the Rays traded him to Oakland.

In 2018, Heim started the year in Double-A Midland and hit a meagre .183 in 39 games before being sent back to Advanced-A. It was there when Heim started to put things together. He went .292/.353/.433 with seven home runs and 49 RBI in 80 games.

During the 2019 season, Heim hit a combined .310/.385/.477 with nine home runs and 53 RBI in 85 games as he rose to Triple-A. His strong season paid off when he was added to Oakland’s 4o-man roster at the end of the 2019 season. The A’s went 97-65 that season and made the playoffs, but fell in the Wild Card Game to the Rays, and Heim did not play.

He finally broke through during the pandemic-shortened 2020 season and made his big league debut for the A’s in August 2020 after seven years in the minors. He played 13 games the rest of the way and hit .211 with five RBI in 38 AB.

Don’t Mess with Texas


In the 2021 offseason, Heim packed his bags once again as he made his way to the Lone Star State in the trade that sent Elvis Andrus to the A’s.

In his first season with the Rangers, he hit a respectable 10 home runs in 82 games but only managed a .196 average. Last season, he had a great first half of the season hitting .262/.313/.467 and 12 home runs and 33 RBI. He cooled down in the second half, only hitting four more home runs, but still finishing with a solid 16 home runs and 48 RBI in 127 games. He raised his batting average for the season to .227 versus the .196 average from 2021

Coming into this season, expectations were still tempered as Heim was expected to split time at catcher with Mitch Garver. However, Garver injured his knee early on and this opened the door for Heim, who has run with the opportunity.

There are a number of factors we’ll examine that have led to Heim’s improvements this year, starting with changes to Heim’s swing.

Swing Adjustments


I stumbled upon some footage that shows five minutes of Heim’s swings back from 2018 when he was playing for the High-A Stockton Ports. Pay specific attention to Heim’s foot placement and movement during his swings.

This is more prominent if you slow down the playback speed, but you can see that Heim’s front foot lifts completely off the ground as he approaches his swing (4:04 mark):










Then as he drops his wrist and turns his hips into the swing, his front foot begins to rotate outwards and it appears his back foot momentarily floats off the ground (4:06 mark):










If we compare those 2018 mechanics to this season, there are noticeable changes; changes which Heim discussed earlier this month with the Dallas Morning News.

During the offseason, Heim did an autopsy of his swing and concluded that he needed to generate more power with his lower body. This year, he has focused on keeping his feet set which allows him to build more force as he swings.

After the Rangers’ 5-4 loss to the Angels on May 5th, Heim explained his approach to the Dallas Morning News. “The way I’m going about my swing, I’m more grounded.” He added, “I’m not moving as much, and I can stay on those pitches a little better.”

Screenshots taken from the 2023 season show there is still a front foot lift, but Heim keeps his front foot closer to the ground and roots his back foot into the ground, giving him a powerful anchor to swing from.


It also appears that Heim has widened and opened his stance this season. Here he is during the Rangers/Yankees on April 30, hitting moon shots from both sides of the plate. His at-bat from the right side of the plate falls just short of a home run, but you can see Heim display a wide stance as he launches the ball.



Heim’s stance and swing adjustments have led to him accessing more of the strike zone, which has led to hitting better against pitches thrown low in the zone.

In 2022, his batting average on pitches low and inside the strike zone was .130, with an expected average of .189. On those same pitches this season, he’s batting .353 with an expected average of .245. That means some regression from the .353 mark is likely, but he is still doing much better against those low-located pitches this season.



Source: Baseball Savant

Heim’s also hitting with more overall power in 2023. His Barrel percentage has improved to 10% which puts him in the 65th percentile of all MLB hitters, compared to 6.9% last season (43rd percentile.)

His SLG is .460 after sitting at .399 in 2022, and his xSLG has jumped to .491 this season (84th percentile in the league) compared to .361 last season and .372 in 2021.

Additionally, he’s getting better contact on the ball. Heim’s launch angle is up slightly this season (18.1) compared to last season (17.0) and his sweet spot% (defined as a batted-ball event with a launch angle of 8 to 32 degrees) of 38.3% puts him in the top-40 hitters in the game.

This is such a large increase from 2022’s number (29.6%) that it puts him in the top ten in all of baseball for the most improved sweet spot%.

Most Improved Sweet Spot % from 2022 to 2023


Improved Approach

Another element to Heim’s progress this season is an improved approach at the plate. His first swing percentage has dropped to 36.1% from 38.7% last season, but when given the opportunity he is also attacking more often. His overall swing percentage has increased to 55.1% from 50.8% in 2022.

Heim has also shown he is a more complete hitter with his results against fastballs and breaking balls thus far in 2023.

Digging deeper into last season’s numbers, as expected, he faced fastballs the majority of the time in 2022 with pitchers deploying the pitch 56.7% of the time. Against the fastball, Heim hit .236 with an xBA of .224, a SLG of .382 with an xSLG of .385, and a wOBA of .305.

Facing offspeed pitches 17.7% of the time, Heim hit .244 with an xBA of .251, a SLG of .477 with an xSLG of .344, and a wOBA of .332.

Compare the 2022 numbers to this year’s statistics below, and you will see Heim has improved against fastballs but is absolutely crushing offspeed pitches in 2023.

Heim vs Pitch Type in 2023


This is the type of seismic change to Heim’s approach that could stick long term. Pitchers won’t be able to fool him as easily with offspeed stuff, which makes him a more dangerous hitter moving forward.

Shifting the Expectations


This is a bit of burying the lede, but another important piece of the Heim-hitting profile is that he switch-hits. This season he is hitting .389 from the right side of the plate and .237 from the left side of the plate.

And as nicely covered in Mark Steubinger’s recent Pitcher List article, Heim is taking advantage of the new rule that bans shifts and this has also led to success.

In 2022, while batting left-handed, Heim faced shifts from the opposing team 78.2% of the time and had a .263 wOBA against the shift. This year, with teams not able to deploy the shift, he has a .318 wOBA from the left side of the plate. With no shift and mechanical changes, Heim is able to pull the ball more freely and with more power. Here is Heim on the left side of the plate crushing a low pitch for an extra-base hit.



And just for fun, if you want to see the full evolution of Jonah Heim as a hitter, here he is 10 years ago as a high school senior.



It seems that Heim is slowing down after a scorching hot start. This would match what happened in 2022 when he had an excellent first half before the bottom dropped out on him in the second half. Perhaps he will develop into a player that routinely comes out of the gates blazing, and he just needs to learn how to keep that momentum going across the whole season.

Some of that slowdown is expected in part to the fatigue that comes with playing the catcher position and the wear and tear that occurs behind the plate. Heim is focused more on his lower body power this season, and playing catcher for a full season takes a toll on one’s legs (Does anyone remember Joe Mauer’s bilateral leg weakness?)

However, Heim has already started three games at DH this season and this could be another option for the Rangers to still get Heim’s bat in the lineup later in the season.

After taking a close look at Heim’s 2023 season, the question remains for both Rangers fans and catcher-hungry fantasy teams: is this for real?

My best guess is that he will level off somewhere between the start of this season and the lows of last season. Heim has overhauled his stance and swing, giving him a better chance at hitting effectively throughout the entire strike zone, and his improvement against fastballs and offspeed pitches shows that he’s developed a more complete hitting package. These changes point to real progress as Heim has carved out a nice role in Texas as he enters the prime of his career at age 27.

Even if balances out to a .240 or .250 hitter with 20+ home runs and 70+ RBI that still makes him a key piece of the Rangers offense and an intriguing fantasy asset. This would put him perhaps a tier below Salvador Perez, J.T. Realmuto, and Will Smith in the hierarchy of fantasy baseball catchers, but not too far behind.


Photo by John Bunch/Icon Sportswire | Adapted by Justin Redler (@reldernitsuj on Twitter)

Nate Kosher

Nate Kosher is based in the Twin Cities and is a staff writer for Pitcher List. He grew up watching low-budget Twins teams at the Metrodome before eventually converting to the Arizona Diamondbacks (the power of teal and purple in the 1990s). His goal is to someday visit all 30 MLB ballparks and he believes Barry Bonds should be in the Hall of Fame. You can read more of Nate's writing in his newsletter, The Relief Pickle.

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