PORT Adelaide young gun Zak Butters is expected to spend about a month on the sidelines after scans confirmed he had sprained the medial ligament in his right knee in Thursday night's 31-point loss to Melbourne.

The exciting forward landed awkwardly when marking the ball in the third quarter and was subbed out of the game.

>>WATCH THE INCIDENT IN THE PLAYER ABOVE

It's a devastating blow for the 20-year-old, who was playing his first game back in more than three months after left knee and ankle setbacks. 

Butters had 10 disposals, four marks, three tackles and two clearances before leaving the field.

Port Adelaide's Zak Butters leaves the field with his right knee strapped in R17, 2021. Picture: AFL Photos

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 clash with St Kilda next week.