A few months ago I was asked to explore the nature of pitch sequencing and why it matters in baseball. It seems intuitive that pitch sequencing is supremely important in the game. We've been told as much by countless broadcasters in both simple ("he needs to establish the fastball early") and complex ("He's used two fastballs inside on him which sets up the slider perfectly here") ways.
I've dedicated a lot of words and creative hours to the exploration of pitch sequencing. I wrote this as a primer of what I hope to accomplish with my research. Note: I owe a lot of credit to Brooks Baseball whose impressive database has made this all possible.
At this point I want to establish how difficult and complex a starter's job is compared to a reliever's.
My personal assumption heading in was that starters have more complex arsenals and need more pitches to survive the workload. A reliever is essentially a two-pitch pitcher whereas a starter needs a deep arsenal.
The two pitchers I used as my examples are Jeff Samardzija and Carlos Marmol. All information posted here is through May 27, 2013 so it's not extremely current but the sample is big enough to display just how different these two jobs are.
Research and results
Jeff Samardzija has developed a fairly complex repository of pitches. As you can see, a batter has to keep several pitches in mind during any at-bat he has against Samardzija.
Marmol is more of a straight up slider monster, albeit a largely ineffective one. The batter can essentially sit on either fastball or slider with Marmol and be right about half the time.
Relievers don't have to face hitters more than once so it's ok if they have a super-simplified plan of attack. Starters on the other hand need to establish a pattern early in the game and then keep the hitter guessing by mixing it up in later at-bats.
A closer look at Samardzija's pitches
This gif is a quick rundown of how varied each of his sequences are. Samardzija does like to double up with his pitches and thus far in 2013 he favors the fastball/sinker to start at-bats more than any other pitch.
It's not shocking that he does, either. Everything works off the fastball as a pitcher. All secondary pitches are simply ways to trick the batter into thinking a fastball is coming when it isn't. The fastball is the most important pitch in baseball and it's the backbone of any pitcher's arsenal.
Let's also take a look at Samardzija's differing plans of attack on an individual basis:
This is an ongoing project, one that won't be completed until the final pitch is thrown in the regular season. What I found here did reinforce my ideas about the complexity of starting versus the relative straightforward nature of being a reliever. I was surprised at how complex Samardzija is as a starter, however.
Samardzija isn't the simple fastball-slider-splitter guy I foolishly thought he was. The splitter is most definitely his strikeout pitch but there's more to his stuff than that. While he isn't at the Yu Darvish level of pitch selection complexity there is some interesting refinement in his approach to attacking hitters.
I suppose it was foolish to think any starter would have a simple arsenal but it was good to see it laid out visually.