The Avalanche was dealt a crippling blow Monday when it was determined that captain Gabriel Landeskog would be lost indefinitely to head and leg injuries, the result of a huge hit he took Saturday from the San Jose Sharks' Brad Stuart. Landeskog will miss Monday's game with the Edmonton Oilers, and the Avs say there is no timetable on his return. The team did not say Landeskog has a concussion, but declined to be more specific than the general term of head injury. The puzzling aspect to Landeskog's sudden sidelining is that he returned to play with seemingly no ill effects early in the second period of Saturday's game, after taking the blow from Stuart late in the first period. Landeskog said he felt good after the game. Landeskog did not practice Sunday, but the team gave no indication he was hurt, and he had already missed a practice earlier this season from a routine "maintenance day." Symptoms worsened entering Monday, however. The Avs already have lost a top forward, Steve Downie, to a season-ending knee injury. Losing Landeskog — the NHL's rookie of the year in 2011-12 — for any serious length of time would be a massive blow to the Avs' playoff aspirations. Based on last year's roster, the Avs are now without three of their top nine forwards from last season in Landeskog, Downie and holdout Ryan O'Reilly.