SBNation.com's Ryan Van Bibber has been ranking NFL position units this week on a team-by-team basis. Specifically, he has been focusing on defensive backs, first ranking cornerbacks and then safeties. Unfortunately for the Detroit Lions, they are pretty far down on both sets of rankings.
On the cornerbacks list, the Lions are ranked 30th in the NFL. Chris Houston is recognized as the team's best cornerback, but beyond him there are a lot of question marks (Aaron Berry, the rookies, etc.), hence the low ranking.
At safety, the Lions are a little higher up on the list at 27th. Here's why:
The only thing putting the Lions this high on the list is Louis Delmas. His attempt to play through a torn MCL in the Lions' playoff loss to New Orleans was disastrous. He is the only player of note in Detroit's secondary. A benching in Week 11 did nothing to help Amari Spievey. Veteran Erik Coleman could grab the starting strong safety role from Spievey, but it is unsure if that is an upgrade.