Ever since Mike Green’s status was called into question earlier this week, due to a virus attacking his liver, the competition for the Red Wings’ final blue line spot has taken on an added dimension.



Previously, there were four young prospects vying for what looked like one spot on the team. Now, it looks like there could potentially be two spots, at least to start. That makes the blueline competition all the more interesting.



Red Wings coach Jeff Blashill has talked openly in recent days about the way he judges players — essentially a running tally of plays that impact the game positively compared to those that do so negatively. Not all impacts are created equal, but the basic idea is he wants players to put themselves in the positive column overall.



It’s a good framework for understanding the preseason, because it identifies what the Red Wings are looking for. These defensemen all have differences in their game, so a sort of...