Joba's Slider

I wanted to take a closer look at Joba’s numbers over the past 3 years to see if anything stood out besides the obvious loss in fastball velocity. Below is some data on Joba’s slider.

Joba’s Slider vs. LHB

	P	AVG	SLG	Contact%	PVX	PVZ	VEL
2008	157	.188	.292	47.1%	7.6	-18.3	85
2009	201	.175	.263	60.6%	6.4	-17.4	85
2010	106	.222	.444	57.6%	6.3	-18.3	86

Joba’s Slider vs. RHB

	P	AVG	SLG	Contact%	PVX	PVZ	VEL
2008	230	.159	.222	47.4%	7.3	-17.7	86
2009	353	.271	.402	63.6%	6.4	-16.5	85
2010	241	.217	.348	64.6%	6.6	-16.7	87

Joba’s pitch count obviously received a bump in 2009 because of the 31 starts he made that year. But overall, batters made better contact on the pitch than in 2008. You can also see that his slider lost a good deal of both vertical and horizontal movement in 2009. He lost nearly a foot per second of vertical movement against LHB and 1.2 against RHB, while losing almost equally as much horizontal movement.

In August of 2008, Joba went on the DL with shoulder inflammation, but returned to pitch in September of that year. I looked at the overall data on his slider in that final month and it was right in line with his pre-DL numbers (PVX of 7.8, PVZ of -18.0). So I’m not sure why he lost so much movement on his slider in 2009, but doubt the injury contributed much at all. I guess he could have been pitching through the injury in September ’08 and only felt the full effects the following season. But I doubt the Yankees training staff would have allowed this to happen. At this point, we can only speculate/complain about the extent his shoulder injury affected his performance.

However, Joba’s heat maps show that location may have been part of the problem with his slider.


You can see that his slider was not dropping out of the zone nearly as much in 2009. It’s possible that since he wasn’t getting as much movement on his slider, it hung in the zone more after 2008. Or perhaps he simply had more trouble locating it in addition to a loss in movement. But it’s pretty apparent that his slider lost some bite after his rookie season.

Granted, it’s really tough to gauge a real sense of progression or decline from these numbers since he bounced between starter and reliever each year. I think it’s reasonable to expect his numbers to regress in his second season with the league getting more looks at him, as well as the increase in work load as a full time starter. But there’s no denying that Joba’s slider was among the best in the league in 2008, and he’s yet to duplicate his success with it since.