Alex Frolov scored the lone Rangers goal last night, and with three of last year’s top five scorers currently out with injuries, that’s probably not the last time you’ll read that sentence. The Avalanche scored two goals in 26 seconds in the third period last night to win 3-1, hours after John Tortorella announced that Vinny Prospal had successful knee surgery and will miss six to eight weeks. (In his absence, Marc Staal wore an alternate captain’s “A” last night.) Among the concerns at this early stage in the season: The power play has just two goals in seventeen opportunities, while the penalty kill (which has allowed six goals in nineteen chances) has given up a game-winning power-play goal in the third period or later in three consecutive games.