Addition by subtraction only works if a player is a bad locker-room influence or has proven that he dragged the team down for years imho, neither is the case with Leino. As absymal as Leinos start to his Sabres-career has been, are we really better off without Leino as we are with him? The current situation certainly doesn't support that assumption, especially our bottom-six (where Leino would probably play) is just bad, we play with 3-5 guys who can do nothing but grind a night (McCormick, Kaleta, Hecht, Scott, Ellis, depending on who is in the line-up), or whole bottom-six barely has any skill and the few Skill-players we use down there are either too small (Gerbe) or too young (Grigorenko) to be effective in that role. And especially Grigorenko is forced to play in the NHL because we just have no better options in our bottom-six with at least some offensive talent, even though he certainly doesn't look like he is ready yet.
Don't get me wrong I have been very disappointed with Leinos first season and him probably missing the whole year now certainly doesn't help. But the team won't get better just because we get rid of a player who isn't playing anyway at the moment. It's not like we would use the additional cap-space for a big UFA-signing anyway, I doubt that any high-profile Free Agents would come to Buffalo at the moment...