Losing AFL grand finalists Hawthorn have bolstered their defence by picking up Western Bulldogs veteran key backman Brian Lake on the opening day of the trade period.

The Hawks gave up their first two national draft picks, No.21 and No.41, in return for Lake and pick No.27.

It strengthens a Hawthorn defence that was seen as their main area of vulnerability in this season's finals.

Bulldogs list manager Jason McCartney said the Dogs were happy with their end of the bargain, as it strengthened their position for November's draft.

They were also mindful that Lake, an All Australian in 2009 and 2010 and the Dogs' best and fairest in 2007, turns 31 before the start of next season and becomes eligible for free agency at the end of next year.

It means the Bulldogs, who are in a rebuilding phase, might have risked losing the 197-gamer at the end of next year anyway and by trading him, get some control over the return they get through the draft.