The following is a guest post from AJ Walsh. You may know AJ from the Cubs blog 'Goat Riders of the Apocalypse". He has also written for Major League Trade Rumors. We are pleased to have him contribute this excellent article on the ever evolvng Starlin Castro. You can follow AJ on Twitter @ajwalsh08.
Starlin Castro's offensive output has been falling since Opening Day. By month, his OPS is down from .784 in April — which is already almost not that good — to .763, to .711, to .687 in July. So much for Anthony Rizzo helping him out over the past 31 days.
That said, I think Castro is improving his core skill set as a hitter this year, and love what I see in a few key trends. How can this be when his OPS has simultaneously fallen from decent to, uhh, no thank you? Let's look at five key stats, all viewable in graph form here: http://www.fangraphs.com/graphs.aspx?playerid=4579&position=SS&page=1&type=mini (Thanks, Fangraphs!)
This is the biggie. For those unfamiliar, ISO measures raw power by removing singles from a hitter's slugging percentage and isolating extra-base hits. To calculate ISO, one subtracts AVG from SLG, leaving only the extra bases earned with the bat. The most powerful hitters can approach .300; for example, David Ortiz is batting .316 this season, and slugging .609, giving him the league's second-best ISO at .294. Hitters without power tend to be at or below .100; Ichiro's .095 ISO this year is a good example.
So where is Castro on this scale? In short, he's climbing the ladder. His ISOs this season by month: .100, .148, .145, .173. And to be even more selective about my small sample, since the break he's at .203. Like I said, climbing. This is especially good to see because he put up a .108 in his rookie year, and a .125 in 2011. And if he's going to be a formidable hitter he needs power. I'd love to see him maintain that .200-ish ISO over the balance of 2012, as I'm sure would the guys in the Cub front office and the other fans in the stands.
2. K and BB
These two we can discuss at the same time; let's start with strikeouts. When Castro was only putting up .108 in ISO, it was important that he cover the plate well and frequently put the ball in play to maintain his offensive value. Fortunately he was able to achieve this in 2010, putting up a 14% K-rate on the year, just under Derek Jeter (Juan Pierre was just above 6%, but most of the league leaders were between 9% and 14%). That rate went down a hair in 2011, before climbing this year — through June 16 (an admittedly arbitrary date), his rate was up above 18%, with 51 Ks in 281 PAs.
You might think it a consequence of his adding power — except that over the past month and change the trend has reversed. Maybe it's too small a sample size to take anything from, but since that game on June 16 Castro's K rate is down to 11.6%, with just 18 Ks in 155 PAs.
Meanwhile, his walk rate — which fell from 5.7% in 2010, to 4.9% in '11, to 3.7% over 2012 — is up to 8.3% over those same past 155 PAs. Both encouraging stuff.
3. BABIP and GB%
There's never been any reason to worry about Castro's BABIP; he was up near .350 for about 1,000 PAs to start his pro career. But over the first four months of 2012: .380, .333, .310, .238. A .238 in July! That's bad! He was above .333 in every month in 2011 save one (.305), and did put up a couple of .270s in his rookie year. But .238! It stands out.
The culprit appears to be a result in batted balls, with Castro's groundball rate climbing dramatically over the last several weeks (refer back to the graphs at Fangraphs, unfortunately I can't find this in number form split up into months). I don't know if that's a random thing? I'm not that smart. But maybe it is? On the full year, anyway, Castro's batted ball types for 2012 are essentially identical to 2012. So maybe he's just been unlucky this month — which would explain the decreased output in terms of OPS, despite the fact that his power is increasing and his K/BB numbers are both moving in the right direction.
Those are, I think, the numbers behind the final output statistics that matter more. I hope you agree that there are some encouraging signs here, despite the fact that Castro's OPS has been in decline since day one of this season.