Who was the opponent when Devin Gardner was the player?
CREATE TABLE "2013_season" (
  "rank" real,
  "player" text,
  "year" real,
  "opponent" text,
  "passing_yards" real,
  "rushing_yards" real,
  "total_offense" real
);
SELECT "opponent" FROM "2013_season" WHERE "player"='Devin Gardner';