Here’s a weird thing about Marcus Stroman’s slider: it has more drop than his curveball. We still call it his slider because it goes four miles per hour faster than his curve, but the curve has slowly tilted sideways. Or, to say it better, Stroman’s other pitches have tilted downwards and the curve has stayed about the same.

Check out Stroman’s release points. For every pitch other than the curve and the sinker, Stroman is an inch or two more over the top this year.

In related news, all of Stroman’s pitches — other than the curve — are dropping more this year.

Marcus Stroman Vertical Movement by Year

Year	Fourseam	Sinker	Change	Slider	Curve	Cutter
2013	9.1	0.0	6.4	-0.7	-3.9	4.3
2014	9.2	3.3	3.9	-1.4	-2.3	4.9
2015	8.6	1.8	3.6	-2.0	-1.1	4.0

SOURCE: BrooksBaseball.net

Movement = PFx_z, or vertical ‘drop’ in inches

Could this just be mucking with classification systems? Maybe. The two pitches are only three mph apart. Let’s look at the movement on both of his breaking balls in one place and see if they’ve moved from last year to this year, then. Use the filter to change years.

Yup. The slider drops more than the curve, and the curve is more horizontal this year. He’s also using the slider more this year, and the curve less. But the whiff and ground-ball rates on the curve are better than they are for the slider.

Going more over the top has increased the ground-ball rate on all but his slider, and that may be why he’s pitching today. Not going over the top as much on the curve has made that pitch more of a frisbee than a round-house curveball.

Maybe he’s still getting his feet under him, and things will change again in the future. But for now, Marcus Stroman may be the only pitcher in baseball that has a slider that drops more than his curveball. PITCHf/x classifies his pitches a little differently, but we can forgive that system. He’s got a strange mix.