ya, detroit had to move one of fielder/martinez -- cabrera at third is a disaster (and begging for injury problems). fielder was hardly better than martinez last year, and has 6 more years and is owed something in the neighbourhood of $140mn more than martinez.
they got a good second baseman with a plus 2b bat, and now have ~$10mn to invest elsewhere in the roster. kinsler's only 2 years older than fielder, and his dollar amount declines in the latter years of his deal.
cabrera/martniez dh/1b next year. they find a 3b who can play D. they spend the savings on the rotation, at third or on an outfielder (keeping in mind, they were about as bad as the jays were in left last year).
this is a good trade for detroit.
from texas's perspective, they have arguably the best prospect in the world right now who happens to play kinsler's position. and, unlike the tigers, have no viable option at first for a team looking to compete.