There is a certain, sad symmetry to it all. Penguins defenseman Zbynek Michalek , who has missed the past seven games because of a concussion, expects to be back in the lineup Friday when they visit the Ottawa Senators. His brother Milan , a Senators forward who had dressed for all 31 of his team's games this season and led the NHL with 19 goals before Wednesday night, nearly certainly will not be in uniform against the Penguins. Because of, you guessed it, a concussion.