NJ - wait a bit. You know that much of Espinosa's value is tied up in his defense,
and you know that the public domain stuff valuing defense is probably behind the Rays proprietary systems and those on the Nats. The rest of his WAR comes from playing regularly and his position. his offense has been worth 2.6 runs for his career.
While it is only 2 years of Shields, his cost is below market for pitchers of his track record, too. It isn't so much "how much more is 4 years of Espinosa control worth relative to 2 years of Shields," it also is "how much more attractive is the Shields contract than overpaying in years and dollars for Greinke (many articles saying he's gettting $150MM), Sanchez, or taking on the risks of Dempster or Haren?"
Finally, if you view Lombardozzi a 2 WAR player if he is full time (basically, replacement level offense, positive defense but not elite, and a regular), you are swapping about 1.5 WAR a year for 2 years of Shields (less what you would have gotten out of a typical #5 starter). It is not as cut and dry as you make it out to be.
As for the morse piece, this in part assumes that ALR is back, so Morse is less of an asset for us and closes the deal for the Rays.