West Coast midfielder Elliot Yeo has been subbed out of his side's clash with Port Adelaide after sustaining a head knock.

Yeo required medical assistance during the second quarter of the match, being assisted off the field following a clash with Power tall Sam Hayes.

The Eagles onballer was seen with a bruise on his right cheek after the collision, with West Coast soon deciding to sub the 28-year-old out of the match.

Should Yeo be required to follow the AFL's concussion protocols, the midfielder will be required to miss the coming 12 days of action, which would include his side's Round 7 clash with Richmond on Friday.

Former Giant Zac Langdon was brought into the match with less than six minutes remaining in the opening half.

The Power had injury worries of their own, with Robbie Gray subbed out of the match for young defender Lachie Jones.

Gray required treatment on his leg midway through the third term, with the Power calling an end to his day with approximately five minutes remaining due to a jarred knee.

Earlier in the match forward Todd Marshall required stitches after a head clash in the second term while defender Aliir Aliir finished the first half hindered, however both were able to continue in the third quarter.