You nailed it, Mike. You trade for Castro this spring. You have 4 years of team-controlled cost, from age 26 through age 30, for a Catcher who is good both with the bat and glove, and has an Oliver WAR projection of 4.7/4.7/4.7/4.1 (not 2 or 3 WAR, as claimed by a poster). (It might cost you Kepler, but not much more, perhaps the Astros would even listen to a trade involving Pinto and a lesser prospect instead of Kepler- you still have Suzuki as a backup this year and Turner on the way soon). There is no "now what?" You have a basic building block in place at a key position for the next run. Now, you begin the search for your next building block, say SS Yunel Escobar as a possible FA, who projects at 3.0-3.5 annual WAR over the next 4 years. (No more wondering if Polanco can or can't cut it at SS). What then? The Marlins refuse to buy out Giancarlo Stanton's arb years, signing him to another one year/$6.5M last month, and it's reported that Stanton still isn't happy with the situation in Miami. Trade the necessary 2 or 3 better prospects to make this deal (it will be costly, but it shouldn't cost you Buxton or Sano), and you have 3 cost-controlled years with a 24-year old guy who is projected by Oliver to produce 4 straight years of 6.0+ WAR (with the chance to buy them out to sign him through age 30). No more wringing of hands about whether there is anybody who can play alongside Buxton when he eventually arrives. And now you have a potential top of the order reading Buxton/Mauer/Stanton/Sano. (Batting behind Mauer and in front of Sano would be the answer to Stanton's dream situation and out of his current Marlin nightmare). These are just examples- and these 3 project to add up to 15 wins, per year, over the next several seasons..... as opposed to "Waiting for Godot" for the Twins Farm to finally all get called up and produce. Even if every prospect works out perfectly on their respective timetables, it still doesn't guarantee a pennant contender any time soon while they transitions and acclimate to the big leagues. For example, the rebuild with the World Series up-and-comers taking their roster spots took 6 years in the 80s and just about as long in the late 90s, early 00s for the perennial division contenders. Getting proven major leaguers to competently plug the holes and the question mark areas can short-cut that process considerably- and in fixing these positions, you aren't spending huge amounts of money that might curtail your efforts at acquiring FAs for other areas of need