Gagner left a game Saturday night after taking a stick to the face from Vancouver Canucks forward Zack Kassian. The Oilers were already expected to be without No. 1 center Ryan Nugent-Hopkins for the first month of the season as he continues to rehab from shoulder surgery.
Taylor Hall is likely to move to center in Nugent-Hopkins' place, but who replaces Gagner remains to be seen. Gagner had 14 goals and 38 points in 48 games for the Oilers in 2012-13, and is in the first season of a three-year contract with an average annual value of $4.8 million.