There's literally nothing to worry about re:Cossa. He's very young at a position that usually takes a long while to develop. A goalies Sv% is also a very noisy stat, given how good or bad a team's defense effects the quality of shots a goalie will see. Just give him time, everybody raves about his character and work ethic.If you look at Cossa from a pure numbers and success standpoint. He's completely on track for a "normal" goalie development curve. I'll be worried when he's 23-24 and still the same goaltender.
I'm not @ing you, just the general concern around him by some Red Wings fans.