Seahawks special teamer Dewey McDonald is believed to have torn his ACL on Sunday, a source tells Ian Rapoport of NFL.com (on Twitter). An MRI today will confirm the injury, ruling him out for the season.
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McDonald is in his second season with the Seahawks, with whom he logged a personal-best 14 appearances last year and played 63.3 percent of special teams snaps. He was retained in the spring as an exclusive rights free agent.
After losing to the Titans on Sunday, the Seahawks are 1-2 through three weeks. Next up is a Sunday night showdown with the Colts.