Image Source: Fox Footy

Kangaroos backman Ben McKay has been subbed out of Sunday's clash against Hawthorn after suffering a knock to the back of his head during a marking contest.

A knee to McKay's head required immediate attention on the sidelines, with the key defender working through a concussion test.

McKay failed the medical assessment shortly after venturing down into his side's rooms and was subsequently ruled out of the match.

The 24-year-old will now be required to undergo the AFL's concussions protocols and will automatically miss the next 12 days of action, ruling him out of a Round 2 appearance against the Eagles in seven days' time.

Should McKay overcome any lingering concussions symptoms, he'll be in line to face Brisbane on Saturday, April 2 at the Gabba.

Young Roo Charlie Lazzaro has been injected into the game as the medical sub, with McKay's day over after recording no disposals.

Hawthorn tall Max Lynch was also subbed out of the match after a nasty collision in the second quarter, having also failed a concussion test.

Lynch was replaced by medical sub Tom Phillips and is now set to miss his side's Round 2 clash with Port Adelaide.