Out of the Arms of Babes

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.

update: some balls in play weren't included from recent games; fixed now and changes noted below

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.

Pitcher	Thr.	G	BF	PT	P/B	P/G
Thomas Diamond	R	1	27	120	4.4	120.0
Mitch Atkins	R	3	32	124	3.9	41.3
Justin Berg	R	26	115	402	3.5	15.5
Jeff Stevens	R	18	82	340	4.1	18.9
James Russell	L	36	150	562	3.7	15.6
Jeff Gray	R	7	45	157	3.5	22.4
Andrew Cashner	R	27	130	471	3.6	17.4
Casey Coleman	R	1	17	63	3.7	63.0
Brian Schlitter	R	7	45	169	3.8	24.1
Esmailin Caridad	R	8	23	97	4.2	12.1

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)
Diamond	89	89	76	81	73
Atkins	89	90	84	83	76
Berg	90	91	83	84	78
Stevens	92	92	85		73
Russell	90	90	81	81
Gray	92	93	86
Cashner	97	97	87	87
Coleman	90	90	82	81	77
Schlitter	94	93	84	86
Caridad	92	92	78

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.

Justin Berg




Mitch Atkins




Thomas Diamond




James Russell




Jeff Stevens




Casey Coleman




Andrew Cashner




Jeff Gray




Esmailin Caridad




Brian Schlitter




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).

Pitcher	GB%	LD%	FB%	PU%	HR/FL%
Diamond	29%	29%	29%	14.3%	0.0%
Atkins	38%	19%	29%	14.3%	10.0%
Berg	47%	18%	30%	4.5%	4.7%
Stevens	41%	16%	38%	5.2%	12.9%
Russell	28%	17%	44%	11.4%	13.0%
Gray	65%	6%	29%	0.0%	8.3%
Cashner	52%	22%	21%	4.4%	15.4%
Coleman	54%	38%	8%	0.0%	0.0%
Schlitter	36%	24%	30%	9.1%	11.5%
Caridad	46%	8%	38%	7.7%	16.7%

updated 910pm

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.

Pitcher	rvERAa	rvERAe	Swing	Whiff	B:CS	IWZ	Chase	Watch	nkSLG
Diamond	3.90	3.07	.483	.310	2.3	.483	.355	.346	.571
Atkins	5.73	5.50	.403	.240	2.1	.532	.207	.396	.571
Berg	4.59	6.50	.445	.123	3.0	.530	.223	.312	.348
Stevens	6.65	4.87	.382	.177	2.6	.453	.168	.331	.690
Russell	5.35	4.50	.496	.233	1.9	.543	.273	.286	.588
Gray	9.08	4.97	.420	.167	3.0	.490	.200	.344	.588
Cashner	5.90	5.21	.427	.254	2.5	.512	.236	.337	.600
Coleman	10.77	8.35	.444	.107	3.3	.524	.133	.227	.615
Schlitter	10.25	6.00	.456	.169	2.8	.515	.195	.291	.834
Caridad	7.76	4.81	.361	.171	2.8	.443	.167	.324	.538

rvERAe, nkSLG updated 910pm

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.

Group	G	BF	PT	rvERAa	rvERAe	Swing	Whiff	B:CS	IWZ	Chase	Watch	nkSLG	GB%	LD%	FB%	PU%	HR/FL%
Rookie Cubs	71	666	2505	6.27	5.23	.440	.203	2.5	.510	.226	.317	.574	43%	18%	32%	6.9%	10.7%
Other Cubs	107	3433	13084	4.26	4.02	.449	.237	2.0	.514	.276	.350	.515	43%	19%	30%	8.2%	7.2%
All Cubs	107	4099	15589	4.58	4.22	.447	.232	2.1	.514	.268	.344	.525	43%	19%	30%	7.9%	7.8%
NL	835	63651	247791	4.28	4.30	.444	.218	2.0	.512	.270	.354	.510	45%	20%	28%	7.3%	7.3%

rvERAe, nkSLG, GB, LD, FB, PU, HR/FL updated 910pm

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.

The Cubs staff is 9 runs better than average in 2010. The non-rookie pitchers have been 25 runs better than average, and the rookies 16 runs worse than average. Those aren't even clean numbers, as relievers and starters are being treated equally. With the exception of Diamond, the rookie innings have been in relief. More so, "average" is not the same as "replacement" so they way we usually convert runs to wins is not what I'm doing here.

runs against average have been corrected 910pm

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.