LONDON -- Oakland receiver Amari Cooper suffered a concussion early in the second quarter of the Raiders' 27-3 loss to the Seattle Seahawks on Sunday after taking a vicious hit from strong safety Bradley McDougald.

Later in the game, the Raiders confirmed that another member of the receiving corps, Seth Roberts, had also suffered a concussion.

Raiders quarterback Derek Carr also left the game with an injury. He was holding his left arm gingerly after getting sacked six times by the Seahawks and wouldn't have returned to the game had Oakland gotten the ball back, though he said afterward he was OK.

Cooper's injury came on an apparent helmet-to-helmet hit by McDougald, who celebrated the play with cornerback Shaquill Griffin. No flag was thrown.

"The big thing right now is I hope Amari is OK...he's a good kid," said Raiders coach Jon Gruden, who added that he thought it was a helmet-to-helmet hit. "Losing Amari the way we did, I just hope he's OK."

Amari Cooper was injured in the first half in the Raiders' game in London. Naomi Baker/Getty Images

Cooper was coming across the middle and reaching down to corral a low throw from Carr when McDougald arrived.

Cooper stayed motionless on the Wembley Stadium pitch for several minutes before being helped off the field. McDougald was later jawing at the Raiders bench.

Last season, Cooper took a similar hit against the Denver Broncos and missed the following week's game with a concussion.

Roberts was hit after making a catch early in the fourth quarter and stayed on the ground. The Raiders confirmed his concussion diagnosis within minutes.

Information from The Associated Press was used in this report.