The 4-3 overtime victory Saturday night in Montreal, when the Penguins overcame a 3-1 deficit, was one of their most impressive of the season. It also might turn out to be one of the most costly. Two defensemen, Kris Letang and Zbynek Michalek , took hits to the head late in the third period, and both will sit out their second game in a row when the Penguins face the Capitals tonight. Although neither has been confirmed to have a concussion, that remains a possibility for both. They returned to Pittsburgh to have their conditions evaluated and monitored.