It seems to me like the line of Briere-Leino-Hartnell does a lot of first man in/first man back, so after the puck drops they're really just forwards.
Leino is often the first man back and covers what is traditionally the center's role in the defensive end when he is. Briere creates a lot of offense from below the opponents' goal line, so he's rarely first man back. Under Stevens, that was a problem and Briere's +/- numbers were embarrassing. Trying to switch off in your own end, when Briere did get back, created a lot of problems.