Taking A Look At Joba Chamberlain's Velocity

Throughout the debate on whether or not Joba Chamberlain should be starting or relieving one thing that keeps coming up is this idea that his velocity suffers in his starts which supposedly means he should be coming out of the bullpen.

While watching games, I have noticed this to some extent, but I am the type of person who doesn’t trust his own eyes. I like to have data to backup my observations otherwise I end up doubting myself. To remove some of the doubt I have this morning I went through Pitch FX and pulled out some of the velocity numbers of Joba’s appearances last season and I put together a couple helpful charts.

Here are the numbers during Joba’s 2009 starts:

I split it up after July because that was the point of the season where his numbers took a nose dive. From the beginning of the season until July 29 he pitched 20 games, all starts, 110.2 innings, a 3.58 ERA, 97 strikeouts and 50 walks. After that he pitched in 11 games, 45.2 innings, a 7.69 ERA, 35 strikeouts and 26 walks, not counting one relief appearance.

His velocity pre and post July 29 drops, but only slightly. This means that the velocity he had out there was not the main factor for the drop in his numbers. Instead it is probably a loss in command as his walk total went up slightly compared to his innings pitched.

Let’s now compare these numbers to his numbers coming out of the bullpen:

Here is where we see the first real difference. In his starts Joba averages 92.47 MPH with the ability to ramp it up to about 95.69 MPH at times. In his bullpen appearances his average jumps to 95.19 MPH hitting up to 96.46. So not only was his average velocity higher in 2009 when he was relieving vs. starting, but he was able to consistently reach higher one-time speeds.

So where does this difference in speed come from? Well the obvious answer is the difference in stamina. Notice the average difference in his fastest pitch during his appearance is only one-MPH, but the average overall difference is slightly more than 2.5 MPH difference.

Conclusion: What this shows me is that it’s not all about velocity when it comes to Joba’s success on the mound. Yes, he absolutely has a higher average velocity out of the pen by about 2.5 miles per hour, but I think the numbers pre and post July 29th tell me more than the difference than between starting vs. relieving numbers. Like I said before, there was hardly a difference in his velocity after he reached 110 innings, but the stark difference in the numbers means that it is probably much more about command and ability to use his other pitches for him than fastball velocity.

It took a little while to pull all of these numbers and I’m hardly a statistician so there is probably something I’m overlooking here. I just wanted to pull the numbers and see if anything jumped out at me. I also wanted to try to get an idea of what the actual difference in his velocity was and not just the perceived difference. Hopefully I can have some other people look at these numbers and point out anything important that I might have overlooked.