PORT ADELAIDE forward Zak Butters will spend about a month on the sidelines after scans confirmed he had sprained the medial ligament in his right knee in Thursday night’s loss to Melbourne.

The 20-year-old landed awkwardly when marking the ball in the third quarter and was subbed out of the game.

Defender Ryan Burton, who spent a period on the interchange bench late in the contest, had precautionary scans on his groin on Friday but is expected to be available for the club’s Round 18 game against St Kilda next week.