40 in 40: Casey Fien

In the modern bullpen, there are a number of architypes that relievers are labeled with. The flamethrower, the LOOGY, the long reliever. And then there’s Casey Fien. His fastball sits around 93-94 mph—merely average by today’s standards—and his only standout skill, his command, doesn’t turn heads like strikeouts do. But the Mariners signed him to a one-year, $1.1 million deal back in December, and with a spot on the 40-man roster, he has a leg up in the competition to fill the bullpen this spring.

A fixture towards the back of the Twins bullpen for the last four years, Fien fits Jerry Dipoto’s modus operandi perfectly. The 33-year-old sports a career walk rate of just 4.8% and is an extreme fly ball pitcher. After seeing a three year decline in strikeout rate, Fien bounced back last year but that success was overshadowed by a big problem with the home run. Those struggles led to a waiver claim by the Dodgers and an eventual demotion to the minors.

So what led Dipoto to sign Fien to a major league deal? If we look past the results and focus on his pitch repertoire, we see some signs of promise. Fien has three pitches, a fastball, a cutter, and a curveball. His fastball is his best pitch and he’s able to generate an impressive amount of whiffs with the pitch. He isn’t using his velocity to blow the pitch by batters, instead it’s the incredible spin rate that fools opponents. Earlier this offseason, Eno Sarris from FanGraphs used spin rate to identify a few underrated free agents. Here’s what he had to say about Fien’s fastball:

“Not only did [Fien] show elite spin for his velocity, but he also had the second-best whiff rate of his career. Sometimes you have to look past the home runs, especially in a 40-inning sample, even when you’re talking about a pitcher who cleared waivers and was outrighted to Triple-A this past September. In a way, this methodology could help future teams identify relievers who still have life on their pitches despite iffy results.”

In that same article, Sarris also looked at spin rates for curveballs and guess who showed up in that sample? Again, quoting Sarris:

“But there in the middle of the list, we have Fien again, who in any other year would probably be headed for a minor-league invite after the year he had. But in the Era of Spin, he might be find himself with a major-league offer in the coming months.”

The prescience of Sarris is impressive. We know that the Mariners front office is very in tune with the latest sabermetric analytical methods. Looking past the results on the field to see what makes a particular pitcher successful can yield unexpected valuations. Fien’s strikeout rate, driven by an improved fastball whiff rate, bounced back enough for the Mariners to take a chance on him this season. It’s not a particularly expensive risk, but if he’s able to maintain a strikeout rate around 20%, he could be a sneaky acquisition that pays off for the Mariners.