Jacksonville safety Dwight Lowery is out with a head injury suffered in the first quarter against Seattle.
Lowery was dazed after the second play of Sunday's game, a running play where Marshawn Lynch gained 2 yards.
Lowery was unstable as he walked to the sideline and was helped to the bench by trainers.
The Jaguars initially said he was questionable, then ruled him out at the start of the second half.
The loss of Lowery left Jacksonville without two starters in the secondary. Cornerback Alan Ball was inactive Sunday.
Seattle wide receiver Jermaine Kearse left with an ankle injury in the second quarter. Kearse came up limping after a 17-yard catch on the sideline. The team said he was questionable to return.
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