Is it possible that the Cubs acquired Kevin Gregg so they could trade the Shark? Gregg has closing experience which means that he could be used in the seventh, eighth, or ninth if needed. If Wood is retained (which IMO is expected) and he and Marmol duke it out for the closer role, then it seems like the Shark is the odd man out, unless the Cubs want to use him for the long relief role. Maybe though, Hendry is planning on using him as a last resort to try and get Peavy if things look bad for the Cubs.
The other option is that the Cubs aren't planning on retaining Wood or fear that they will lose out on him.
Just speculation but when I heard that the Cubs got Gregg, this popped into my head