One Reason To Still Be Bullish On Erik Swanson
Erik Swanson has been beaten up in his last couple outings, bringing his ERA up to 6.62. And you’ve probably seen him referred to as a "secondary piece" in the James Paxton trade, but don’t underestimate him. If you’re reading a fanpost on Lookout Landing, you’re probably familiar with Swanson’s excellent strikeout and walk rates. And indeed, that’s the main reason why I’ve been high on him. But here, I want to draw your attention to an even less heralded aspect of Swanson’s game: his infield fly rate.
To state the obvious, infield flies are the best kind of contact for a pitcher because they’re practically automatic outs. Sometimes, you even get two outs! Though other times, your first baseman is Eric Hosmer. They’re basically as good as a strikeout. (To be sure, sometimes people drop a pop-fly like Hosmer, but don’t forget that the dropped-third-strike rule means strikeouts aren’t outs 100% of the time either).
Good pitchers get pop-ups. To wit, of the pitchers who threw more than 100 innings last year, the top ten in pop-up rate include Jacob deGrom, Max Scherzer, Chris Sale, and Justin Verlander.
So how good is Swanson? Really good. Over the last three years, his infield fly rate has ranged from 22.5% to 31.2%. For context, in 2018, the MLB average pop-up rate for starters was 10.1%. It was 9.5% in each of 2015, 2016, and 2017. We’ll get back to that.
For even more granular context, you’d want to look at the average rates for the leagues that Swanson pitched in. If there are league-stats for minor leagues, I can’t find it. Instead, I looked at each league he pitched in, and set the minimum innings pitched at 50 as proxy for the starters (I set it at 40 for his stint in the Eastern League in 2018 since he pitched 42.2 innings there).
Here’s what I found: In the South Atlantic League in 2016, Swanson pitched 96 innings across his time with the Rangers and Yankees single-A affiliates. His IFFB% was 31.2%, which ranked 8th of the 134 pitchers to throw 50 or more innings. At high-A in 2017, he got pop ups on 25.4% of fly balls, good for 45th of 135 in the Florida State League. In the AA Eastern League in 2018, his rate was 30%, ranking 7th of 146. And after his promotion to AAA, his rate declined to 22.5%, but it was still enough to rank 15th of 119 International League starters.
That’s a lot of numbers in one paragraph, but let me put it this way: on average, he’s ranked in the 86th percentile. Really good. Pop-up rates can be a little bouncy, and it’s more stable for hitters than pitchers, but over a 3-year, 311.2-inning sample, it’s telling us something.
As to how he’s pulling it off, my strong suspicion is that it’s because of the rise on his fastball. Sitting at 92-95, and rushing up to 98, it’s already coming in with a lot of heat, and with that apparent burst right before it crosses the plate, hitters are getting underneath it. That’s magnified by Swanson’s tendency to throw his fastball up in the zone. Yesterday, Nomar Mazara popped up on a four-seamer located here:
And Rougned Odor popped up pitch number 3 here (though it went just out of play), another four-seamer:
And this brings me back to the 2018 jump in the MLB pop-up rate. It could be single-season noise. (There was also a spike in 2011 that turned out to be nothing.) But it could also be a side-effect of the fly-ball revolution. As hitters try to increase their launch angles ever further, it stands to reason that they’d get too far underneath it more frequently too. So Swanson could be perfectly suited to the times.
One final thing to keep in mind is that while the infield fly is about as good as a strikeout in terms of results, they’re much more valuable to a team because they take fewer pitches on average, and, more crucially, they cost less. Arbitration is notorious for rewarding traditional, counting statistics like strikeouts and ignoring rate stats, especially batted-ball rates. Since the Mariners have control of Swanson for three arbitration years, his pop-flies will help the team while keeping his costs down. Even if the new CBA alleviates this somewhat, we shouldn’t expect a total reversal. So don’t give up on Swanson just yet.