Let's look at Jason Castro's defensive ability through three main categories
Some questions are as old as time. Things like "the chicken or the egg" or "has this milk really gone bad?" will continue to puzzle people long after we're gone. The question I'm after today is a bit different. I'd like to know just how much of an impact Astros rookie Jason Castro has had defensively.
The reason is pretty straightforward. When he was about to be called up, there were plenty of scouting reports touting his defense. Some went so far as to predict a Gold Glove in his future at some point, while others were much less encouraging. Those said he'd be a below-average guy and might have to be moved off position.
Certainly, Castro's bat hasn't been what's kept him in the major leagues this long. He's batting just .200/.283/.292 this season in 156 plate appearances. That's well off his minor league averages and I'm confident he'll rebound offensively once he's given some time to adjust. Plus, he's just 23 years old. He has plenty of time to start hitting.
No, the thing we're only starting to get a handle on his his defensive abilities. Watching him before his call-up this season, you could see the potential there. He gunned down some incredibly fast players like it was nothing, famously catching a guy stealing at third base in the 2009 Futures Game.
Now we have a little more information to build upon. Still, what makes up a catcher's defensive ability. With other positions, you can look at things like double plays turned or outfield assists to figure out how good a guy might be. With catchers, there are so many different aspects to their skill.
Do you like Legend of Zelda? Of course you do. Who wouldn't? I'm going to arbitrarily bring that up to create a Theory of Catching Defense that revolves around three things: arm strength/steal deterrence, blocking abilities and calling a game. Using those three categories, we'll look at Jason Castro's rookie season to see how he stacks up both against the league and against his own team.
How's The Arm?
In 350 innings over the course of 47 games at catcher, Jason Castro has seen 576 stolen base opportunities. That's an average of 1.64 opportunities per inning. The major league average is 1.58, meaning teams are in position to steal slightly more often for Castro than the rest of the league.
Around the league, teams try to steal about 5.99 percent of the time they have the opportunity. With Castro, that number falls slightly to 5.34 percent. Without even looking at his caught stealing percentage, it's already apparent that teams respect Castro's arm.
Luckily, we do have some numbers to see just how good his arm has been. Castro has gunned down 12 runners out of the 31 stolen base attempts this season, which is 39 percent of the runners. That's a great percentage, one that Ausmus was only able to beat four times in 19 years. The league average is 28 percent and only four other catchers with as many innings as Castro have a better mark.
The Ausmus Test
Since I mentioned Ausmus, we should bring up the next set of defensive criteria, which is inspired by the former Houston Gold Glover. Ausmus was a master at blocking balls in the dirt. He did it mainly by deadening the ball with his chest protector, pouncing on it after it died in the dirt.
Castro is a bigger man than Ausmus and it makes sense that a bigger man would have a harder time moving lithely behind the plate. Castro also is a relative newcomer to the tools of ignorance, so he's still learning some of those techniques. If there has been any criticism of the boy wonder, it's this. Castro definitely has a problem blocking balls in the dirt.
In those 350 innings, he's allowed four passed balls and 19 wild pitches. Now, the vagaries of these definitions mean that it's hard to say whether some of those wild pitches were his fault. For our purposes, we'll look at both numbers on a league average to get an idea how he's done.
The league is averaging 0.396 passed balls plus wild pitches per nine innings. Castro's average works out to 0.596 per nine innings. For once, the stats back up what the eyes have told us. Castro isn't very good at blocking balls yet, but he's young. There's always time for improvement.
Calling A Game
The third leg in our tri-force of catching defense is how he calls a game. That's most easily reflected in catcher's ERA and catcher's Runs Allowed. It's not a perfect measure, since there's a lot that goes into calling a game, but it's the best we have.
Castro sports a cERA of 4.01 and a 4.78 catcher's Run Average. The first is below league average by 0.10 runs while the latter is above league average by 0.33 runs. So, Castro helps his pitchers give up slightly less earned runs than average but can get in trouble with errors and unearned runs. At least his own errors aren't causing the spike in Runs Allowed, since Castro has yet to commit an error.
His Q Score
Since the Astros have another catcher renowned for his defense, it might be instructive to compare Castro to Humberto Quintero. Let's start with Q's arm, since he recently showed it off so well against the Phillies.
Q has also thrown out 39 percent of possible base stealers, nabbing 19 in 49 attempts. He's played in 533 innings this season and seen 5.88 percent of his stolen base opportunities convert to a steal attempt. That's still below average but not by a lot and more than Castro.
Where he really shines is in his blocking skills. Q has only had four passed balls and nine wild pitches in almost 300 more innings than Castro. That's an average of .219 unblocked balls per nine innings, which is quite a bit less than the league average and almost a third of what Castro is averaging. The funny thing is both Q and Castro have been charged with four passed balls. The difference is really apparent in the wild pitches charged to both players. Most catchers see a lot of wild pitches and some have no hope of being stopped. Still, there may be something to Q's ability to stay away from these.
Q has also been extremely successful in cERA (3.98), lower than both Castro and the league average. His catcher's Run Average (4.40) is also less than both Castro and the league. Basically, Q is solid at both throwing out out baserunners, blocking balls in the dirt and in caling a game. He's the perfect defensive specialist as the backup catcher. Castro, on the other hand, is just as good in only one category (arm), slightly worse in another (calling a game) and significantly worse in a third (blocking).
FanGraphs has a lovely little stat that ties all this together in their Wins Above Replacement statistic. It's the fielding component. Right now, Castros has been worth two runs above replacement defensively. There are only 11 other catchers in the league who can say the same, and some of them haven't played as much as Castro. It hasn't helped his overall value any, but by any measure, Castro has been very good defensively this season.
The problem is, only two catchers have been better than Humberto Quintero defensively this season: Russell Martin and Miguel Olivo. Neither Q nor Castro are hitting the ball well, meaning it comes down to who has the most defensive value and how the Astros want to bring Castro along. Right now, that probably means continuing to split time with Quintero, but after seeing Kevin Cash play for part of this season, fans really do deserve the excellence they're seeing behind the plate in Houston.