The article by Farhan Lalji mentions that the Canucks could be looking for a puck-moving defenceman to anchor their power play.
However, the Canucks had also been in the market for a top-six forward but, given the play of Ryan Kesler and Alex Burrows since moving up to the top two lines, that may not be as pressing a need. But by moving those two players up, the third line has become significantly weaker, so a depth-type of checking player may be someone the Canucks are looking for.
A 3rd line player/checker would be more my guess as well. But don't expect Gillis to give up anything higher than a 2nd round pick for that. More on Lalji's opinion here.