In yesterday’s post I theorized that Kevin Slowey had terrible overall starts whenever he gave up a run in the first inning. This was proven to be true; however, I didn’t look into what caused the bad starts, only that they happened. So, what was the cause of these poor starts?
My theory yesterday was that because Slowey is a control pitcher, his command must have been off. But it could be a number of other reasons as well, including pitch selection, velocity, movement, lefty/righty splits, and batted balls. I’ll look at each of those below, starting with control.
Control: It appears that Slowey did struggle with control on his change-up (CH) and curveball (CU). In starts where he didn’t allow a run in the first inning (now called NR1) he was able to get strikes on 33% of CH’s and 46% of CU’s. In games where he allowed a run in the first (now called R1), his strike % declined to 24% for the CH and 34% for the CU. Obviously there’s some strategy that changes game to game, but when games are grouped like this it suggests some level of difficulty controlling those pitches.
Conversely, as you’d expect, Slowey threw his fastball and sinker a couple percent higher for strikes in R1 games. I say ‘as you’d expect’ because if he’s having difficulty throwing his off-speed pitches over for strikes, he’d be forced to get strikes by throwing the hard stuff into the zone.
Pitch Selection: This was almost exactly the same between the NR1 and R1 starts. The strategy going into the game, in terms of pitch selection, doesn’t vary significantly, so the fact that he threw 3% more sinkers and 4% less sliders does not provide any additional insights into Slowey’s struggles.
Velocity: Another non-factor. The largest variation of any pitch was on the slider, which Slowey threw 0.6 mph faster in R1 starts.
Movement: Movement can be somewhat tied to control. If the pitch is moving more than Slowey expects, he’s obviously going to have some problems pinpointing the pitch where he wants. So it’s no surprise that the CH and CU provide the greatest difference between the NR1 and R1 starts. As compared to the NR1 starts, Slowey had 37% less movement on his CH and 74% more movement on his CU. That level of variation may make it difficult for Slowey to adjust, forcing him to throw more fastballs for strikes.
Left/Righty Splits: Both lefty and righty batters increased their AVG and SLG significantly in the R1 games. For lefties the rise in AVG/SLG went from .247/.368 to .351/.571, while for righties it increased from .259/.412 to .371/.771. Both lefties and righties hit better in R1 starts, so there’s no definitive cause here.
Batted Balls: Batted Balls is more of an effect than a cause of the issue, but it does show some interesting results. The groundball % remained the same between NR1 and R1 starts. However, there’s a significant swing in the flyball and line drive rates. In R1 starts the LD% increased from 18% to 25%, while the FB% declined from 39% to 28%. This is an important difference because batters hit an overall .240/.230/.552 on FB’s and .752/.752/1.069 on LD’s against Slowey. Thus, even a 7% increase in LD’s can have a large effect within a game.
In summary, it looks like Slowey had control and movement issues with his change-up and curveball in the R1 starts. This resulted in a lower percentage of CH and CU being thrown for strikes, allowing hitters to wait on the fastball and sinker and hit those pitchers hard (.355/.559 AVG/SLG on fastballs and sinkers combined in R1 games versus .266/.411 in NR1 games).