Plus/minus is not a perfect measure but looking at expected +/- gives is a better look into the Philadelphia Flyers plus/minus stat.
First here is how expected +/- works : Metrics utilizing league-wide shot location data, show what we’d expect each Flyer’s player’s +/- to be at season’s end, based on where his team’s shots and his opponent’s shots came from while he was on the ice in even strength situations. The expected value of these shots is based upon league-wide shooting percentages from the various locations (www.sports-reference.com).
The Philadelphia Flyers stat sheet this season is filled with some big minuses in the +/- category.