Throw strikes. It is the simple, yet effective mantra for pitchers of all ages. But eventually, the really good pitchers begin to learn secondary pitches such as sliders, curveballs and changeups. Suddenly, throwing strikes isn't as appealing anymore. From a young age, pitchers are taught that hanging, or leaving secondary pitches up in the zone is an easy way to give up extra base hits.
Because MLB hitters are very good at squaring up baseballs, some pitchers have to live on the corners and/or outside of the strike zone. Masahiro Tanaka is one such example, as he has had a below average Zone% every year of his major league career. Because hitters have famously teed off against his fastball and sinker, he is forced to depend on his slider and splitter more than he would probably like.
Tanaka is one of several pitchers who is in a kind of No Man's Land with his fastball. His fastball's velocity, spin rate, and extension aren't excessively extraordinary, which is a Statcast-friendly way of saying he isn't a "stuff" guy. According to Baseball Savant, hitters have a .249 batting average with a .425 slugging percentage against Tanaka's pitches in the strike zone. They also have an average exit velocity of 93.4 mph, 100th place out of 110 qualified hurlers.
Another similar pitcher is Cubs starter Jason Hammel. After struggling with the Rays, Rockies, and Orioles, he joined the Cubs and promptly ramped up the usage of his slider:
He has shown flashes of dominance since joining the Cubs, even though he has the bad habit of collapsing in the second half. This year, his ERA sits at just 2.36. The interesting thing about his slider is that he isn't even a little afraid to throw it in the strike zone. Pitch F/X has the Zone% on his breaking ball at 44.7%, which is close to the league average for all pitches. Against sliders in the zone, hitters have a .175 batting average and an 89.7 mph average exit velocity.
They are getting a few extra base hits, with a slugging percentage of .368, but Hammel's slider is giving him something he can use for damage control when he has to attack the strike zone. Despite costing him an estimated 41.1 runs over his career, FanGraphs' pitch value metric has his four-seam fastball's worth at 5.2 runs above average in 2016. It is possible that hitters know they have to be ready for the slider in the strike zone, which helps him use his other pitches more effectively.
On the other hand, there are pitchers like Michael Pineda who aren't so lucky when throwing their secondary pitches in the zone. On sliders in the strike zone, hitters have a .373 batting average with a .644 SLG%. He throws his slider in the zone about 31% of the time, clearly for a good reason. At the same time, someone like CC Sabathia has managed to revive his career with his new cutter. FanGraphs categorizes it as a normal fastball, but he uses it to attack the strike zone at a 51.2% clip.
Pounding the strike zone with secondary pitches can seem counterintuitive, and for good reason. However, for pitchers who lack electric stuff or a deceptive arm angle, cutters, sliders and curveballs located in the strike zone can be just enough of a change of pace to limit the damage done from having to throw strikes. With metrics like spin rate and extension, it will be interesting to see if teams tell pitching prospects to work on throwing sliders or cutters in the strike zone. Hanging sliders are undoubtedly very dangerous, but the tradeoff can be worth it.
Data is courtesy of FanGraphs, Baseball Savant, and Brooks Baseball.