Turning double plays. It seems like every 2 out of 3 double play chances are accompanied by "And the throw to first... not in time." It has be be difficult to keep saying over and over again and not get sarcastic about it.
I have no insight as to why. Barney and Castro are both good defenders. Possible things that can go wrong:
The throw to the second base bag is off target so the fielder gets off balance catching it.
The throw to first might be in the dirt and not handled cleanly
The balls are hit too tricky to get two off of, maybe they are slower, or the fielder has to range away from the bag to field it.
The fielder is slow at transitioning to throw the ball.
I really don't know what the answer is. I just wish it wasn't true. It could be luck on hits or it could be something fundamental.
Quick note on fangraphs UZR fielding scores,
Darwin Barney is a well-above-average fielder, but has a negative double play score.
Castro has good range but has made lots of errors, and has a slight negative double play score.
That doesn't really explain anything, but reaffirms that they are indeed bad at double plays. Let's just hope it's bad luck on screwier than usual hits and it will change the rest of the season.