This might not seem like a big injury, but Gostkowski was one of the better kickers in the league at getting touchbacks, from what ive heard, shayne graham isnt a great kickoff guy, and his range isnt as good as gostkowski's either, this means alot for field position and close game situations.
as to who the patriots would have had to release to make room for graham in the event that Gostkowski was ok? dunno, seems like everyone is making a contribution this year, the patriots utilize alot of their roster to house developmental players who are too valuable to them to cut, wheatley for instance they had to value at least a little bit and he was practice squad eligible, unfortunately he was picked up by the jags, but it doesnt matter how many other FA corners you bring in here, if the patriots get another injury at corner (i think Arrington is hurt now too right?) all they have left is Wilhite and butler (who for some reason is completely shut down).