It's a risk but I like it for the Rangers. Swapping Kin's contract for Fielder, along with the money Detroit is sending, means the Rangers are on the books for $76 million more than they would be otherwise. That's a of a lot cheaper than giving Robinson Cano $275 million.
Fielder is only 29 and should bounce back due to:
1) Moving from Comerica Park, which is on lefties, to the Ballpark and its home-run porch should mean an increase in production is already built-in.
2) A big part of why he had a down year last year was that that they had a top prospect named Avisail Garcia that was porking Fielder's wife. Fielder found out about it, demanded they trade him (which the Tigers did), then divorced his wife. So I can understand how that sort of thing would affect a player's preparation and focus.
And you open up a spot for Profar at second base. He was a replacement-level player last year as a rookie and should only get better.