Browns wide receiver Mohamed Massaquoi and tight end Benjamin Watson have sustained head injuries and will not return to Cleveland's game against Seattle.
Massaquoi and Watson were both injured in the closing minutes of the first half.
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Massaquoi was hit by Seahawks cornerback Brandon Browner on an incompletion over the middle during the second quarter. The Browns announced at halftime he would not return.
Early during the third quarter, the team reported the injury to Watson. It's unclear when Watson was injured, but it's not believed he came out for the second half.
Last season, Massaquoi missed one game with a concussion after he was hit by Pittsburgh linebacker James Harrison, who was fined for the helmet-to-helmet blow.
Seahawks cornerback Walter Thurmond was announced as doubtful to return with an ankle injury.
The Associated Press contributed to this report