Looking at BP's metrics on Castro, they show him as below average for throwing and blocking, which is confirmed by the metrics you'll find anywhere else. For 2016, they show him as having saved 17 runs (a career high) with his pitch framing which I don't think would amount to 0.22 ERA among the whole staff -- perhaps 0.02. Comparing to Suzuki, Castro is a huge drop off for blocking but otherwise he is an improvement. So as long as Berrios, May, etc., can find the strike zone this year, Castro will be an upgrade defensively. Neither of them are good at throwing, but Castro is better. I would call Suzuki the "safer" catcher, good to pair up with a wild pitcher. Castro is the guy you want paired with your top starters. He can get that extra strike out of an umpire if the umpire is already liking who is on the mound. With the current Twins pitching situation I'm not sold on Castro being the answer. As for his bat, Castro has more potential than Suzuki, but at the end of the day the results from the both of them are a bit even with Castro being good at some things and Suzuki being equally good at other things. Castro could have a break out year though. Suzuki's break out year is behind him.