Cooper was running a slant pattern from the right side of the field and the ball was thrown high from Derek Carr when Broncos safety Darian Stewart arrived and hit Cooper in the neck and head area. Stewart was flagged for unnecessary roughness.
"It was a vicious hit," Del Rio said. "The kind we're trying to remove from our game, quite frankly. You see less and less of those. I'm sure the league will take a hard look at it. Those are the kinds of impact hits that don't need to be a part of our game right now. The guy is clearly defenseless and got targeted right in the head. There's a chance to hit in the strike zone and be somewhere else and not be there like that."
A cart drove on the field to take Cooper off but the receiver, who appeared to be knocked out in the immediate aftermath of the play, walked off the field with help. He was later ruled out with a concussion.
He also sprained his ankle on the same play, a source told ESPN's Adam Schefter.
"Anytime I throw a ball and I feel like I had anything to do with it, it rips my heart out," said Raiders quarterback Derek Carr. "I'm not even going to lie, I had to hold back the emotions of him getting hit and thinking it was my fault. The way the linebacker played it, I had to throw it where I had to throw it. But anytime he gets hit, I feel terrible."
Carr said center Rodney Hudson had to shake him out of it.
"[Hudson] saw it on my face and said, 'Hey, man. Shake it off. We gotta win this game.' I was like, 'You're right. I'll be good. But that's my brother.'
"I hope that he will be OK. I know he will -- I talked to him."