Detroit's borrowing against the future - they're banking on getting a third round compensation pick for Suh, but instead of having two third-rounders next year, they traded next year's third to pick up a fourth round pick this year, which turned out to be DT Gabe Wright.
They've re-tooled the offensive line - it's much younger - and grabbed a corner in the fourth round. But Mayhew traditionally doesn't do so well with later-round picks, except Theo Riddick, I think.