Feelings about the Mariners’ rotation right now range from significant trepidation to torches and pitchforks right-side-up tridents. Last year was a disaster of historic proportions (remember the three weeks where Yovani Gallardo was the de facto No. 1 pitcher? The White Sox remember), and the design of this year’s rotation doesn’t feel dramatically different. With over a month of transactional inactivity on the 40-man roster, the entire rotation is getting a tacit vote of confidence from Jerry Dipoto and the front office, to the chagrin of many fans. Through that support, no player on the Mariners, or perhaps in all of baseball, should feel more emboldened by this winter’s inactivity than Marco Gonzales.

After years of being rushed, converted, injured, and shuttled, a spot in the Opening Day rotation is the newly 26 year-old Gonzales’ to lose. To best measure Marco as a Mariner, we’ll have only Spring Training data to work with, along with his work last year. While that’s not much, a couple things - pitch velocity and mechanics - are entirely within his control, and they’re what we should be tracking most doggedly this spring.

I listed several sets of numbers in Marco’s 40 in 40, but the pair we’ll dwell on are 92.1 and 94.0. Those are Gonzales’ average and maximum fastball velocity in 2017, per Brooks Baseball. Both are career highs, up from an average of 90-91 and a max of 93.3 mph during his time in St. Louis, pre-injury. That’s good news! Even better, the significant upticks in velocity occurred after Gonzales joined the Mariners in August. Whether by work with the Tacoma/Seattle coaching staff or his own adjustments, Gonzales was throwing at least two mph harder than he was as a rookie, and earning his fastball greater room for error as a result.

We can go to film and see a difference mechanically that backs up the radar gun. First, a couple fastballs from Gonzales in his most successful start as a pro, back in September of 2014:

The delivery is compact and more 10/12ths than three-quarters. This near-over-the-top release is short and direct, almost like an infielder’s motion. Marco’s leg lifts while facing up and down. While it’s certainly possible to generate high velocities from this sort of release point, doing so usually requires a violent motion (think Shae Simmons). In the game above, Gonzales’ fastball averaged 89.97 mph. In contrast, just 4.3%(!) of the fastballs Gonzales has thrown so far in Seattle were under 90 mph. What changed? His mechanics, and somewhat significantly!

Here’s Gonzales’ fastball on September 29th, in his final start of the season, against the Angels:

There are several things to see here! This fastball was clocked at 93 mph, and Gonzales averaged 92.4 mph during this start. His throwing arm takes a longer path than before, moving downwards out of his glove, then backwards and upwards in a C-shaped motion, instead of the concise straight backwards movement seen in St. Louis. Marco’s motion as a whole seems elongated, as if he’s attempting to generate more power, and his leg lift is noticeably higher. Finally, his release point is further out from his body and lower, as his arm slot is now somewhere between 3/4ths and sidearm. Thankfully, we don’t have to rely on our eyes alone.

Statcast has tracked the release point of every pitch Gonzales has thrown since his debut in 2014, and, frankly, the difference is even greater than I expected. The gif below shows every MLB pitch Marco has thrown. The first image (the one including “Intentional Ball”) is his release point as a Cardinal, from 2014 thru his first start in 2017, while the second flips to all 10 of his appearances as a Mariner:

That’s striking. Gonzales’ release point on fastballs has shifted roughly an entire foot since he joined the Mariners, and his curveball and changeup have followed suit to some degree. Interestingly enough, Gonzales’ shift in arm slot resembles that of another Mariners lefty who unlocked extra velocity by dropping their arm angle: James Paxton. Gonzales’ fastball has benefited, and if he’s able to throw 92-93 mph fastball, he should be better equipped than ever before to have success with his calling card change-up...

...or he would be, if his change-up’s velocity wasn’t increasing at an even greater rate.

A healthy difference in velocity between a fastball and a change-up is usually 8-10 mph. While Mariners fans have been spoiled by Félix’s unique style, most pitchers can’t get by with just 6-7 mph difference between their heater and change. When Gonzales first was called up, he had about a 10-11 mph separation between the pitches. That, combined with impressive sinking action, led scouts to call his change-up an elite pitch. Let’s go back to that 2014 start vs. Colorado:

78 and 79 mph, with that same compact release that gets on top of the ball. Now here’s Gonzales from August, 2017:

The pitch is still excellently located, and Manny Machado rolls over on it for a groundout. But the release is different. Further extended from his body, Gonzales seems to be “behind” or “inside” of the ball, meaning the spin (and resulting movement) runs more horizontal instead of sinking. Again, we can see his release point with St. Louis vs. now:

That, along with the increased velocity, has shifted Marco’s deadly change-up into a pedestrian offering. Without an adjustment, Marco may struggle to generate the results he’s used to with his go-to offspeed. In looking at video of late 2017, when Gonzales located his change-up low and out of the zone, it retained excellent sink, but to be effective he’ll need that consistently.

Improved velocity on the whole is a positive sign. The difference between being an 89-91 nibbler and a 91-93 lefty is potentially the difference between Gonzales being Dillon Overton or a solid MLB starter. Gonzales’ struggle to feel for his change-up isn’t surprising considering the apparent shift in his arm slot, but reconnecting with a pitch he’s had mastered his whole career is an easier task than adding velocity is for most pitchers. If Gonzales can combine both, he’s a lot closer to the mid-rotation arm the Mariners so desperately need.

When Gonzales makes his appearances this Spring Training, keep an eye on his release point. Is he more consistent now, another year removed from surgery? Watch the movement on his change-up - does it sink with consistency once again, or still run flatly? And most of all, watch the velocity, and the separation between the fastball and the change.