Intra-division trades between hated rivals are rare, but they do happen on occasion. There was the famous 1964 deal in which the Chicago Cubs sent Lou Brock, Jack Spring and Paul Toth to the rival St. Louis Cardinals for Ernie Broglio, Doug Clemens and Bobby Shantz. Even the Boston Red Sox and New York Yankees have negotiated deals including the infamous Babe Ruth trade.
This means that there are certainly grounds for the Tampa Bay Rays to trade one of their top starting pitchers to an American League East rival. Jason A. Churchill of ESPN (Insider required) has noted that both the Yankees and the Red Sox have an interest in James Shields.
It seems to be difficult to see the Rays as sellers at this point in the year, as they are right in the thick of the Wild Card race. However, it is possible that the Rays can trade Shields while also improving their chances at making the playoffs this season.
Tampa Bay would be a much better team if it could find an upgrade at catcher, first base, shortstop, outfield or DH. It could also go after a second baseman and move Ben Zobrist into the outfield full time.
Chris Archer could re-join the Rays' starting rotation, or the team could insert Jeff Neimann back into its rotation once he returns from an injury (h/t Danny Knobler of CBS Sports).
Boston seems to be a good fit for a deal with the Rays. A possible Shields deal could be centered around Ryan Lavarnway, and the Rays could also ask for first baseman Lars Anderson in addition to a reliever such as Junichi Tazawa.
This deal or a similar one would seem to work for both franchises. It would give the Red Sox the No. 2 starter that they are looking for while helping the Rays immediately fill a number of holes.
A deal with the New York Yankees seems much harder to fathom. The two teams do not match up as well. The Yankees have a number of young outfield prospects that are still a ways away from the majors as well as a number of high-level pitching prospects that have struggled.
If the two sides were to discuss a deal, the Rays would certainly want one of Manny Banuelos or Dellin Betances as well as a young prospect like Tyler Austin. This deal would not put the Rays in a position to make the playoffs this year.
While a deal between the Rays and one of their division rivals seems to be unlikely, there is a better chance that they can work out a deal with the Red Sox than the Yankees. If it turns out that the best deal that the Rays can make involving Shields is with the Red Sox, then they should not be afraid to pull the trigger.