The 21-year-old England striker has broken a metatarsal for the third time in three years and is expected to be out of action for at least two months.
Ferguson told the Herald: "These things happen in football.
"The way the game is, the competition levels and the speed, you are going to get injuries throughout a season.
"For my last five and six years we have had several players injured at all times so that is why you need squads of 23 or 24.
"The important thing is not to panic in these situations. I always believe if we have 11 players fit to go on the park then we believe we can win the game.
"That never changes from me."