Edwin Diaz’s adjustments in 2018 set up future success

Edwin Diaz has become widely known the last two and now into three seasons for his blazing fastball and knee-buckling slider. Many know he was once a starter in the minors and the Seattle Mariners changed him into a reliever. Jake Mailhot over at FanGraphs covered that in an article a few days, so I’m not going to talk about that. Instead what I am going to talk about is how he’s being a bit overlooked this season as Diaz hasn’t been getting the love he deserves. With guys like Josh Hader and Aroldis Chapman doing what they’re doing, many aren’t talking about Diaz as much as they should be.

In his third big league season, not only is he blowing away hitters at a 37 percent clip, but is also walking less than ten percent of his batters as well. There’s no denying Diaz has well established himself as a solid reliever in his time with the Seattle Mariners, despite a slight slump in his sophomore season during 2017. Although by definiton it may not be a slump, his numbers regressed in several key area’s between his rookie season in 2016 and his second season in 2017. Batters started making better and harder contact with pitches Diaz threw both in and out of the zone and they swung less often on both as well. A very low batting average on balls in play of .236 doesn’t really suggest a season of unlucky outcomes, but his home run per flyball rate has consistently been above league average even in his rookie season.

The slump is a bit puzzling, but so far this season he’s basically matching that incredible rookie season in 2016 which put him fifth in the Rookie of the Year voting. He has dropped that home run per flyball rate, lowered his hard contact plus he’s getting more swings in misses on pitches out of the zone while throwing less total pitches in the zone. This tells us he’s fooling hitters with more pitches out of the zone. That’s beneficial because if a batter were to make contact with a pitch out of the zone, they’re less likely to do significant damage or damage at all.

This leads me to ask, what is Diaz doing or not doing that has turned around the areas in which he struggled last year? He’s certainly gotten more comfortable with his slider, throwing it around ten percent more often this year. Part of the increased usage is that he’s getting better break on the pitch and as a result more swings and misses, but more on that in a second. His wOBA off the slider in 2017 was .196, this season it’s .187. So it has gone down, but just slightly, and it was never very high in the first place.

There’s one huge change I’ve noticed that has put him on the fast track to even further success. According to Baseball Savant, last year he threw a total of two four-seam fastballs the entire season, where as this year he’s throwing 45.5 percent four-seamers and only about ten percent of the two-seamers. Even more telling is the sequencing of the two-fastballs. Last year he threw the two-seamers in every count given that was his primary pitch. This year with his fastball being primarily four-seamers, he can attack hitters early.

Baseball Savant

The location tells us even more. Last year he threw the two-seamer all over both in and out of the zone, given that was really his only fastball. This year with him throwing primarily the four-seamer all over the place, he can attack hitters in the zone or close to it with the two-seamer giving him a swing and miss secondary fastball that he can pair with his slider to increase his strikeout rate. And he has. Not only has his wOBA off the two-seamer dropped from .323 in 2017 to .219 this season he’s incased the whiff rate from 13.5 percent up to 20 percent on the pitch.

Baseball Savant

The success of his fastballs and slider this season seems to at least partially come from a slight change in release point. He’s brought his release point down and out away from his body. This seems to have allowed him to get better command and some additional sharp break on his pitches. According to BrooksBaseball, he’s added over an inch of vertical movement on the slider and two-tenths of an inch horizontally.

Baseball Savant

Those two changes, give and change in results like what you see below.

Adapting to the batters early on in his career who have adjusted to him after a stellar rookie season speaks volumes on Diaz’s intangibles and his willingness to evolve and change in order to remain successful. Even a struggling pitcher with that type of a mindset and baseball IQ has a promising future in the majors, now imagine someone with the raw stuff and the solid numbers Diaz has on under his belt. It’s simply incredible to me and I have no doubts that he will be among the top relievers in the game for many years to come. The future is Edwin Diaz’s.

Ron Wolschleger is a pitchaholic and a Contributing Writer for Beyond the Box Score as well as Bless You Boys. You can follow him on Twitter at @FIPmyWHIP.