clock menu more-arrow no yes mobile

Filed under:

Erik Swanson has a great fastball, now we’ll see what he can make of the rest

The distant third pitcher in the James Paxton trade has all the pieces to start and succeed.

MiLB - (Louriann Mardo-Zayat)

“Oh yeah, he’s way better than those guys.”

That was the response a scout gave me when I asked about how Swanson compared to other pitchers the Mariners have acquired in the past three years. Mariners fans have seen a revolving door of players tabbed with the No. 4-5 starter label over the past few years, particularly as Jerry Dipoto desperately attempted to raise to baseline competency of the Mariners’ 25-man roster to support its stars and scrubs core. Since 2016, we’ve seen the Mariners move to acquire a multitude of young players with that designation. Nate Karns, Zach Lee, Paul Blackburn, Ariel Miranda, Rob Whalen, Max Povse, Chris Heston, Dillon Overton, and Chase De Jong all fit the bill. With the exception of Povse, each of the players above has left the organization at this point, most with little in the way of positive results to show. That’s why, like many M’s fans, it initially didn’t move the needle when RHP Erik Swanson was announced as a secondary piece in the Mariners’ return for James Paxton. But that first quote from a scout, and the subsequent research on him, encouraged me to think there’s a stronger player than expected in the Mariners new No. 11 overall prospect.

In prospect evaluation, for as many ways to construct analysis as there are, today I’ll simply start with a pros/cons list.


  • 92-95 mph four-seam fastball, clocked up to 98 mph.
  • Slider & Changeup with good velocity separation.
  • Positive reviews both publicly and privately about his work ethic.
  • In 115.0 IP between AA (42.2) and AAA (72.1) in 2018, Swanson ran a 133/29 K/BB.
  • Is big
  • Reportedly has both a deceptive delivery and a high spin rate fastball that seems to deliver functionally.
  • Has an “Invisible Fastball” according to Yankees in-house media:


  • Durability has been an issue - 121.2 IP in 2018 a career-high, missed significant time in 2014 and 2015 with a forearm injury.
  • Seems to be prone to injury when around other new Mariners prospects:
  • Has been pegged as a “control over command” guy in past.
  • Age 25 means older for a prospect than ideal.
  • Low groundball rate in 2018 is of note.
  • Fastball is clear carrying pitch, secondaries are still only potentially starter-quality.

Listed above is, generally, what Swanson brings to the table. His fastball is a legitimate pitch, and it’s clear from any video footage that it has “rise,” “carry,” or any other term commonly used to high-spin fastballs that sink less than expected due to their ability to counteract air resistance more effectively. You can see that below as he causes Red Sox top prospect Michael Chavis to whiff right through one at the letters:

Swanson fastball

And again, here, Swanson jams and pops up a rehabbing Rafael Devers, who he would eventually strike out.

Sometimes command, sometimes control.

This is, generally, the result Swanson gets with his fastball. It’s his best pitch, and he throws it frequently and in all counts. That pitch helped Swanson run a bevy of impressive numbers in both AA-Trenton and AAA-Scranton/Wilkes-Barre. A 29.6% K% in 115.0 IP between the two levels is impressive, as is a 3.86/3.63/3.55 ERA/FIP/DRA in his 72.1 IP in AAA. If you’re reading a scouting report here, you’re likely familiar with at least the first two metrics listed above, but Deserved Runs Average (DRA) is a slightly less commonly referenced metric. The stat is on the same scale as ERA and FIP, it is simply a Baseball Prospectus-generated metric that tries to go beyond simple fielder reliance (ERA) or fielding-independence (FIP) to get at what a pitcher “deserved” in terms of credit or blame for their work. Quality of contact is increasingly viewed as something pitchers do in fact have control over, and DRA attempts to quantify things as such, along with a myriad of other variables as you can see through that link.

Most importantly, while it is still limited in its scope by what data it receives, it is about as sophisticated as public pitching metrics get for evaluating minor leaguers. To frame the discussion in hopefully an even simpler way, among pitchers with a minimum of 70 innings in AAA this year, Swanson had the 15th-best DRA of all pitchers, and 12th-best of those who were starters in at least 70% of their innings. That list has some names you might recognize from prospect lists (Dakota Hudson, Corbin Burnes, Sean Reid-Foley), others with recent MLB stints (Josh James, Matt Wisler), and a pair of veterans who are former and current Mariners MiLB arms, respectively (Casey Lawrence, Tommy Milone). Showing well at age-25 in AAA, then, is great, but obviously no guarantee of MLB translation. Swanson is older for a prospect because injuries held him back for the first couple years of his career, so he could be viewed developmentally as less fully-formed than the average 25-year-old, but there are still warts that make some scouts, like FanGraphs’ Kiley McDaniel, see a reliever.

The concern for scouts like McDaniel rests on a couple things. First, as I’ve mentioned, Swanson can drift away from command and settle into control. Sometimes that manifests harmlessly, like this fastball that misses up but results in a pop-out because, as discussed earlier, his fastball is legitimately quite good.

Typical batted ball result on Swanson

While this was a slightly missed spot, Swanson was coached to make an intentional effort to pitch up in the zone this year. That plays to his strengths with a seeming high-spin fastball generating pop-ups and fly outs often, with just a 36.4% GB rate. It’s a strategy we’ve seen with Nick Vincent for years, but it also is the opposite of what many pitchers are taught for decades, which could play a role in Swanson’s occasional challenges with command over control.

That’s how a pitcher with just a 4.8% BB rate can average less than 5 and 1/3rd innings per start in AAA. I saw Swanson go to two or three ball counts often, before fighting back with his fastball, typically. The Mariners have had great success refining command in pitchers at the AAA and MLB level in recent years, and Swanson has more velocity and ability than many of their previous options, but it’s still a challenge to overcome.

The other concern is that Swanson’s secondary pitches lag behind his heater. Part way through 2018, he scrapped his curveball for a slider, which is his 3rd-best pitch at the moment but has potential to improve. As of now, it’s got decent late break, but doesn’t give a devastating appearance on film, nor glowing reviews from scouts.

Swanson slider

The third offering is a changeup, which makes sense given Swanson’s four-seam-heavy repertoire. Most reports call this his best secondary offering, and based on the film I saw I’m inclined to agree. Again, this isn’t a Félix level cambio, or even Marco Gonzales level, but with an 8-to-10 mph gap in velocity and good arm-side run, the changeup is both a good change of pace and, crucially, deceptive enough to trouble lefty hitters.

Swanson changeup

What we’re left with is a 4th/5th starter profile unlike those the Mariners have been a turnstile for in the past three years. Swanson’s peripherals look like those of an able starter, who could step in and be a productive pitcher in 2019. But his injury history and slightly labored pathway to those peripherals make him out as more Erik Bedard (or Nate Karns) than innings eater. That’s okay though, especially in the era of longer bullpens and Kaleb Cowart’s. If Nick Vincent is any indication, a pitcher whose fastball is always higher than hitters think it is will do quite well in Safeco Field, and the Mariners could see him as a great candidate to develop a cut-fastball, much like Paxton, Vincent, Gonzales, and Wade LeBlanc. Swanson will be given the chance to start games, likely first in Tacoma, then Seattle soon afterwards, and I think he will ultimately succeed. Of one thing I am sure - between Braden Bishop and Ian Miller in Tacoma, and Mallex Smith and Mitch Haniger in Seattle, the outfields of the organization should be prepared to chase some fly balls.