Marco Gonzales is Worthy of Becoming the Mariners’ Ace

While Mitch Haniger and Edwin Diaz are reportedly drawing heavy yet (so far) spurned interest around the league, Marco Gonzales remains more quietly unavailable. The Mariners know they must take a step back in 2019, but they know Gonzales is a piece they could build around.

Don’t get me wrong —  Marco Gonzales is not an ace. But by dealing James Paxton, the Mariners have left him atop their rotation’s depth chart talent-wise, and he finished out an impressive first full major-league season like he had something to prove.

Over his last four starts, Gonzales sported a pristine 1.71 ERA and 2.73 FIP, owing much of that success to his renewed stinginess in and around the zone. And that was an important development because those last starts followed his return from the DL for a neck strain.

Health is obviously important to every player, and it is undoubtedly so for Gonzales as he relies on the coordination of his body to successfully wield a repertoire lacking a truly dominant pitch.

Following a string of twenty straight 5+ IP starts from April 24th to August 13th, Gonzales dropped his truest dud of the season when that neck injury exacerbated what ended up being a 3-inning, 11-hit, 8-run clunker against the Astros.

The impressive command is typically a given for Marco, but clearly, it is a pre-requisite to his success too.

If we snoop around the beginning of that streak though, we turn up something as interesting as his ability to command the ball.

Prior to that streak, Gonzales relied too much on an average-at-best four-seam fastball.

He threw the pitch upwards of 20% of the time in each of his first four starts according to Brooks Baseball, but on April 24th that trend suddenly evaporated when just 5 of his 89 pitches (5.6%) were four-seam fastballs.

Following that, he threw more than 10% four-seamers in just three starts and we can see the overall transformation quite clearly below.

It seems like it took a few live games for Gonzales to figure that his four-seam fastball was worth ditching for the most part, and that proved true as hitters ended up slugging .480 against it over the course of the year.

That adjustment immediately paid dividends in the efficiency of his innings and consequently, the length of his outings as well. And as the season bore on, more trust was put into his cutter instead.
Gonzales’s cutter is more sneaky good than spectacular, but he spotted it well with increasing consistency. With solid spin and bite, that let it play up to a nifty a .274 expected wOBA compared to the league average of .316 for starting pitchers according to Baseball Savant.

In more tangible terms, batters hit .224 and slugged .397 against his cutter and that success could in large part be attributed to a continually improving feel for the pitch.

Against right-handed hitters, Gonzales initially tried to work exclusively inside with his cutter — granted, we’re talking about a 37-pitch sample — but after he eased off his four-seamer, he began to work more often to both sides of the plate.

It took until the second half of the season for Gonzales to really nail down his approach, but the middle image in the above gif suggests some signs of it being hammered out on the fly.

And the benefits of that change seem obvious with just a cursory look at his pitch mix.

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While Gonzales approaches each handedness differently, from late-April he managed to throw four of his five pitches within one percentage point of 23% of the time overall. Besides being pretty remarkable in itself, that guile was presumably a key part of his success in tandem with an improving cutter.

Eventually, he began consistently back-dooring his cutter for a strike. He started it middle-middle and had it bite right in on the hands. He even started it on the black and dropped it toward the bottom of the zone.

At his best, he seemed to toss that cutter anywhere he pleased.

Meanwhile, that righty wouldn’t know if that 88 mph cutter is actually a 90 mph sinker about to dart away from him or an 85 mph changeup that’ll fade the same way — let alone a straight 91 mph fastball — until it’s too late.

That’s part of what made Marco Gonzales so good.

A more deft approach helped him drop his cutter’s expected wOBA against right-handers from .306 through June to .221 the rest of the way. And over the same time periods, his cutter helped his overall expected wOBA against right-handers drop from .323 to .273.

Unfortunately, he still got knocked for a .309 wOBA despite that improvement, but that could indicate some positive regression ahead in terms of improved batted ball luck if he can replicate the same command.

If he can maintain this adeptness, his cutter is a plus pitch, and it won’t hurt that his curveball has developed impressively as well.

Coming into the season, Gonzales was known for his changeup and that’s about it. Nobody knew how far a new cutter would take him; nobody knew his curveball wouldn’t be far behind either.

You might have gotten the sense that something was up though when, for better or worse, he immediately began to throw his curveball a lot more frequently after being acquired from the Cardinals.

Turns out the Mariners might have picked up on something useful there.

Gonzales allowed a below-average (but not terrible) .289 wOBA/.284 xwOBA on his curveball in 2018, yet it generated an extremely high 74.1% groundballs per ball in play, which certainly helped him escape a jam or two.

A large contribution to that may be well represented by Quality of Pitch (QOP) — a pitch evaluation statistic which “incorporates MPH, location, and movement (vertical break, horizontal break, breaking distance, and rise).”

Based on QOP, Marco’s 5.42 QOP Average for his curveball was 5th in all of baseball among pitchers who threw at least 100 curveballs, ranking behind the respective curves of Rich Hill, Seth Lugo, Tyler Olson, and Aaron Nola.

Whether or not you buy into the model, that is good company to keep on the basis of any statistical mumbo-jumbo.

With a cutter that looks like a plus pitch and a worm-burning curveball supported by a comfortably average or better changeup as well as a sinker and occasional four-seamer, Gonzales has the makings of a deep and effective repertoire.

So long as the command is there, he should be a solid mid-rotation arm, but there is a non-zero chance that he becomes (or arguably remains) one of the more valuable starters in the game.

The fastball adjustment described earlier preceded 25 starts totaling 150 IP (612 batters faced) and a 3.60 ERA/3.59 xFIP.

For comparison, only 30 starting pitchers faced at least 600 batters in 2018 and logged an ERA south of 3.60.

Slap on a requirement of at most a 3.59 xFIP and only 18 starters make the cut.

Whether that is his true talent is debatable, but certainly, the upside is there.

Although his season was not without its low points, Gonzales predominantly showed that he belongs among the league’s better starting pitchers.

Based on runs allowed, his 2.5 rWAR won’t wow you, but his FIP-based 3.6 fWAR, places him 23rd on the 2018 SP leaderboard, sandwiched between Dallas Keuchel and Clayton Kershaw and a negligible distance away from James Paxton.

His DRA-based 3.33 WARP ranks him similarly high at 31st among all pitchers in the league with Dallas Keuchel again just above him and Kyle Freeland just below.

Simply, even if we don’t give him credit solely for the work he did after adjusting his pitch mix, Gonzales still ranked among the league’s more valuable starting pitchers in 2018.

But, of course, there are more ways for him to go than up.

Although his cutter mostly took off from July, one half-season improvement — however impactful — doesn’t paint a complete picture.

Gonzales became more homer-prone around the same time. Couple that with a 27 point jump in BABIP and it’s not a total shock that he posted a 5.23 ERA after the All-Star Break.

Potentially, fatigue set in as he pushed then exceeded a career-high in innings pitched that he set way back in 2014, but he definitely comes with fewer guarantees down the stretch. That is particularly true with his injury history.

Anything short of a successful second half in 2019 may call his durability and ultimately, his upside into question.

Proving to be a great mid-rotation arm or a little better will depend on how deep he can effectively pitch into the season in addition to the continuing mastery of his stuff as the league adjusts to his stochastic approach. He has already struggled with homers the third time through the order.

Whether you reference some advanced statistic or just your eye though, there are plenty of ways to think more fondly of Marco Gonzales than his second half sputtering or a potential propensity for home runs, especially considering he accomplished all of this in his first full season in the majors.

The Mariners have a tough road ahead of them as they perform a high-wire act between building and rebuilding, but perhaps, there is some real inclination to believe that the bulk of expectations for the starting rotation in 2019 and beyond rest on one very capable shoulder.