Trading for major bullpen arms quite often turns into bad investment. For every Andrew Miller (some may say this was not a good trade), there are many disasterous ones like Jorge Lopez, Heathcliff Slocomb, Larry Anderson, Eric Gagne, John Rauch, so on. Trading for elite relief pitchers sounds good yet many of them they do not work out well. It is much better to develop them or make low key moves. Look at the Orioles bullpen or the Yankees. Very good bullpen arms without investing heavily into them. Kimbrell signing was an out of character siging for Elias.