It’s time for a changing of the guard at the top of the Pittsburgh Penguins blue line. The Pittsburgh Penguins defense has been decimated by injuries over the past five weeks. It appears to be trending in the right direction. With Jeff Petry and Marcus Pettersson returning to the lineup and Kris Letang not far behind, the Penguins could potentially have a fully healthy defense core to start the post All-Star break schedule. Fortunately, the Penguins won’t have to wait to figure out who should be at the top of that lineup. For many years the top defense pairing was…