Carlton tall forward Levi Casboult will miss six to eight weeks after suffering a hairline fracture in his left leg in the opening minutes of the Blues' two-point win against Port Adelaide.

The injury, which happened at the top of his tibia bone, does not require surgery.

Casboult hyperextended his knee after talking a contested mark over Tom Jonas, and was helped from the field by trainers.

Andrejs Everitt took the kick after the injury and put through a goal.

Television shots later in the first quarter showed Casboult in the Blues rooms with his knee iced, and no longer wearing his jumper.

He was No. 1 in the competition for contested marks coming into the game and has kicked six goals this season.