Thomas Diamond's impressive -- and bullpen sparing -- MLB debut marked the tenth appearance by a rookie pitcher for the 2010 Cubs. As of this writing, there are six rookies currently on the staff. That number will probably stay there while the revolving door shuffles guys between Des Moines and Chicago. Maybe the number of rookies will be seven or five for a day here or there. Maybe more. However you slice it, the Cubs have a very young group of guys, mostly in the bullpen.
By the time you meander your way through this, you'll know who these kids are, what they throw, how they've performed and, most importantly, who they've performed relative to an "average" National League pitcher and relative to their veteran teammates. In other words, we'll see how much all these kids have cost the Cubs in terms of wins and losses.
Before going too far, you may want to check-out this handy reference at Hardball Times. It contains definitions for almost all the stats and pitch types discussed below. Stats covered here but not there will be explained here. You may notice the last table in this article will be a lot like the first one at the reference link, but with more recent data.
Cubs 2010 Rookie Pitchers - Playing Time
This will give you an idea of how small the individual samples are and how right-handed this group of rookies is. This numbers only include pitches captured by the PITCHf/x system and does not count pitch outs, intentional walks or anything that was simply not recorded.
G games, BF batter faced, PT pitches thrown, P/B pitchers per batter, P/G pitches per game
Cubs 2010 Rookie Pitchers - Pitch Types and Speed (mph)
Now the fun begins. This only covers 2010, so guys like Gray are not a complete picture. This is just a matrix of pitcher and type, with the average speed at release for each pitch, graphs follow with more details on speed and spin.
|Pitcher||4-seam fastball (F4)||2-seam fastball (F2)||Slider (SL)||Change-up (CH)||Curveball (CU)|
Cubs 2010 Rookie Pitchers - PITCHf/x Charts
As usual, I've tossed the Gameday classifications and use my own. These charts, in case you're wondering, are generated in R using templates based on Dave Allen's work, if I'm not mistaken.
Some of the groupings may look odd, as the data is not corrected for camera alignment issues etc. Classifications are generally done on a game-by-game basis, which usually takes care of that in terms of accuracy of my labels. For each pitcher, you'll get two charts. Speed and spin axis is first, it shows the velocity of a pitch and the angle of the axis of the ball's spin. That may be meaningless, so the charts are labeled by direction of break. The second chart throws speed out and breaks spin into two components. The horizontal and vertical spin deflections are shown in inches, from the catcher's perspective.
If these look like Rorschach tests to you, just scroll down past them for more numbers and a little commentary.
Cubs 2010 Rookie Pitchers - Batted Ball Distributions
Remember, we're dealing with some silly small sample sizes that get smaller when it's just balls in play (including home runs).
Cubs 2010 Rookie Pitchers - PITCHf/x Metrics
The rvERA shown in the Hardball Times article on benchmarks is a combination of two other metrics, rvERAa and rvERAe. "a" uses actual outcomes on batted balls, hits and outs as they actually happened. "e" ignores actual outcomes and uses the linear weights associated with batted ball types, liners, pops, flies and grounders.
Cubs 2010 Rookie Pitchers vs. Others
Here's where we get into some larger sample sizes, especially when we look at the entire National League. This is a big roll-up of all the pitchers above, plus the rest of the Cubs staff and the aforementioned senior circuit.
In a nutshell, the kids take an above average staff (warts and all) and make it below average. How much? It sorta depends on how you look at it. Let's do some quick back-of-the-envelope math.
First, the Cubs defense has been sub-par in 2010. Baseball Prospectus has them fourteenth in the NL in defensive efficiency. This screams "use fielding independent metrics". In my case, that's "e" linear weights which are based on batted ball types and ignores actual outcomes. Even home runs per ball in air are regressed to league average with the "e" metrics.
Without doing the calculations of leverage and all that good stuff, I'll say the Cubs rookies have been two wins below average in 2010 (roughly 10 runs per win, depending on run environment). A check of Fangraphs shows the rookies around 1.8 wins below replacement (which is not the same thing as average, and the park adjusted FIP they use is not equivalent to my "e" metrics).
OK, so that was a lot of work to do what took 15 seconds at Fangraphs, but I enjoyed the ride. I do end up understating the quality of the Cubs veteran pitchers, though.
But this is about the rookies. They've been about a two win cost so far. With more and more rookie innings to pile-up, things could get worse, or, if the kids adapt, better. Even if this youth movement, forced or otherwise, costs the Cubs three wins by the time October rolls around, it will probably be worth it. It's not like they'll finish three games out of first place. Maybe out of fourth place.