There is a "player progress" report for all players on your team while playing in franchise mode, that lists all of the players ratings from the year before. Sadly, it's for your franchise team's players only that you can get info.
Once you trade or FA sign someone you can see if they got any better or worse over the past year.
While not being able to see others ratings is a bit of a problem, at least you can save right before making a trade or claiming a FA, so you can undo the deal via a reload.
While this sounds cheesy, in some respects, I've noticed that the computer A.I. knows who's getting better or worse in it's trade A.I., and weighs the players somewhat on that basis. Thus it knows more than we do when making deals, so it's not cheesy or cheap.
On the same note: Good work by the developers... one less exploit as many sports games trade routine A.I's that I remember, don't take this into account when making trade decisions.