For decades, the Red Wings blue line has been patrolled by some of the greatest defensemen in the history of the game. From Red Kelly to Mark Howe to Chris Chelios to Nicklas Lidstrom, the Wings have almost always had a defensive stalwart or offensive game changer on the back end. When Lidstrom retired in 2012, the Wings blue line was left with a gigantic hole. Niklas Kronwall did his best for a couple of seasons, but as age catches up to him, he's lost a step, leaving more concerns surrounding the Wings blue line.