Carlton defender Lachie Plowman has seen his day ended prematurely, after suffering a knee injury early in the second quarter of the Blues' clash with Collingwood at the MCG.

Plowman jumped up in the air to smother Josh Thomas' shot at goal, and came down awkwardly, before yelling out in pain.

Carlton doctors tried to assist Plowman off the field, although the key backman was in too much discomfort, and needed to be stretched off the field.

It's Carlton's second injury of the day, after forward Levi Casboult was withdrawn minutes before the bounce after breaking his finger in the warm-up.