Guillermo Heredia Is Failing to Further Adjust for the Mariners

SEATTLE, WA - APRIL 16: Guillermo Heredia
SEATTLE, WA - APRIL 16: Guillermo Heredia /

It’s been a long and ugly stretch for Guillermo Heredia following a red-hot start to the season. While his early performance hinted at improvement, his .185/.229/.252 (33 wRC+) line over 146 PA since May 28th has chipped away at any confidence in his bat. Pitchers may have adjusted quickly to his success, and that strong initial impression just hasn’t resurfaced yet.

As much as I want it to happen, Guillermo Heredia isn’t going to consistently OPS over .850 like he did over the early part of the season. It took him hitting nearly .300 and walking like Joey Votto to get there. But it’s not like it was all an accident. Suddenly, Heredia was just (relatively speaking) slamming the ball.

As long as he’s been around, Heredia has shown off his eye at the plate. He may seem jumpy at times and he might take some lunging swings, but he generally offers at strikes and is stingy with his swings outside of the strike zone.

Unfortunately, that didn’t help him too much last year, as his patience arguably gave way to passivity and his eye could only afford him a below-average 6.3% BB%. And perhaps the Mariners wanted more out of Heredia’s discipline this year because he has adopted a more “selective-aggressive” approach so far.



Pitch Info’s Plate Discipline stats show that while Heredia has swung at about the same rate as last year overall, his willingness to go outside the zone is at a career low while he is more likely than ever to swing at balls within the zone.

This new approach likely helped drive his early success, as he started jumping on more fastballs.

Among balls Heredia put in play in 2017, 70.4% (228/324)  were either a 4-seam or 2-seam fastball, sinker, or cutter.

Among balls Heredia put in play through May 27th, 2018, 77.1% (54/70) were of the fastball variety. And perhaps more notably, 4-seam fastballs accounted for 45.7% of his balls in play early this year whereas they accounted for only 36.1% of them last year.

With a greater focus on fastballs and being aggressive on strikes, through May 27th, Heredia was able to hit line drives and fly balls at 90.4 mph on average — nearly 2 mph higher than his average last year — and accordingly, his .383 xwOBA easily dwarfed last year’s .277 mark.

He obviously has hit a long cold streak, but even overall, Heredia has a .305 xwOBA that suggests he has markedly improved since last year based on his walks, strikeouts, and quality of contact. And it’s not just the increase in walks. He has already Barreled more balls (6) than he did last year in half the chances and his xwOBAcon (xwOBA on contact) has jumped from .285 to .331.

But most of that was due to his early success when he was destroying fastballs.

Pitchers are still challenging him with fastballs inside the zone (they have to throw strikes somehow!), but on the edges and outside of the zone, they’re recently opting for more breaking balls.

TimeframeFastball Pitch%*Offspeed Pitch%*Breaking Pitch%*
Through May 27th 48.4% 8.8% 16.8%
Since May 28th 41.7% 8.1% 22.0%

Part of Heredia’s regression involves some good fortune reversing, but receiving more breaking pitches around the zone has likely hindered his performance against more challenging fastballs. Unsurprisingly, on fastballs on the edges and outside of the zone, his wOBA has dropped from .493 to .276 since May 28th.

(Over)simply put: The less often he’s able to expect a fastball, the harder it becomes for him to hit a well located one or lay off a poorly located one. And the fact that he’s struggling against breaking pitches this year is just icing on the cake for opposing pitchers.

Slider Pitch Chart vs. RHP
Slider Pitch Chart vs. RHP /

Although he hit .294 on breaking balls in 2017, Heredia is hitting just .096 on them this year, and much of that can be attributed to sliders against which he has managed to hit only .105 after hitting .385 against them last year. As seen above, part of that is due to RHPs locating their sliders on or past the outer third of the plate with greater consistency.

This has particularly been a problem because, since Robinson Cano’s suspension, Heredia has been thrust into the starting CF spot.

Since May 14th (the day after Cano’s last game), 70.5% (136/193) of Heredia’s PA have come against RHPs compared to 40.7% (24/59) prior to that date, and similarly, 73.6% of all pitches thrown to him have been from RHPs compared to 40.6% before.

While he hit righties very well early on, they did hold him back with breaking balls and have resorted to those pitches more often lately.

Through to May 27th, RHPs threw Heredia 22.7% (54/238) breaking balls.

Since May 28th, RHPs have thrown Heredia 32.0% (127/397) breaking balls.

Lefties have had similar success using their breaking balls against Heredia, but with a smaller sample of pitches and plate appearances, it’s more difficult to tell whether they’re beating him or he’s beating himself. Since he’s comparatively always hit lefties well over his short career, it’s possible Heredia is mentally carrying his struggles over to the other handedness.

Because he recently can’t get anything going in upwards of two-thirds of his plate appearances (save for a home run off Andrew Suarez), his issues could stem partly from confidence, overthinking, pressing, etc. as well.

Whatever the case may be, Heredia has looked overexposed at the plate.

He may truly have a new approach and that truly may allow his skills to play up when he gets pitches to hit, but right now he’s facing even more right-handed pitching than last year and they’re working him. Both right- and left-handed pitchers have now beaten him. To get back on track, Heredia needs to readjust.

Just looking at his Swing% by zone on curveballs and sliders, we can see that as his skid progressed, he started opening up the bottom of the zone.

Swing% vs. CU/SL
Swing% vs. CU/SL /

Initially, Heredia mostly kept his swings on curves and sliders to center-cut and elevated pitches, but as the gif flips to the middle part of the season, the bottom corners and areas below the zone light up.

Since his cold streak began, Heredia has started obliging pitchers on more breaking balls in locations that he can’t do much with.

Given that he’s seeing and swinging at more breaking balls on the edges and outside the zone, it’s no wonder that he has struggled so badly. And for what it’s worth, the percentage of his balls in play that were fastballs has dropped back down to 71.0% (76/107).

But this recent lack of discipline is not the precedent Heredia has set. The solution isn’t just “take more breaking balls,” but it might be as simple as that.

If he can resume laying off these pitches, his production should improve against those pesky curveballs and sliders — at least ones he puts in play — and he’ll get more chances to chop at fastballs.

In that case, the walks could return and the strikeouts could simmer down. If he can close the gap on his .361 xSLG too, Guillermo Heredia could really breathe some life into the bottom third of the Mariners’ lineup. It’s all on him to adjust again.

All stats referenced prior to games 07/25/18

*Pitch% on the edges of the zone and outside of it

Fastball: 4-seam, 2-seam, sinker, cutter

Offspeed: Changeup, Splitter, Screwball, Forkball

Breaking: Slider, Curve, Knuckle-Curve, Eephus, Knuckleball