Referee knocked out cold with brutal helmet hit

Now that is definitely going to leave a mark!

Veteran gridiron referee Ron Cherry has been knocked out cold after being caught by a freight train of a hit from USC linebacker Michael Hutchings.

The 21-year-old Hutchings had just helped the Trojans sack rival Notre Dame quarterback DeShone Kizer late in the third quarter when he got a push in the back by a teammate towards the sideline.

Coming the other way at great speed was Cherry.

The collision was a sickening blow with the Cherry coming off second best as he accidently cracked straight into the helmet of the 98kg, 185cm Hutchings.

The whistle blower looked to be in all sorts of trouble as immediately fell to the ground and lay motionless.

But after a few minutes, Cherry was able to get back to his feet and walk off the ground with the help of medics from both sides.