Lions coach Dan Campbell said No. 1 receiver Tyrell Williams is in concussion protocol after leaving the game following a helmet-to-helmet hit in the third quarter.
Williams retreated to the locker room, accompanied by trainers, following the play. He returned to the bench area a few minutes later, but never re-entered the game.
The Lions relied heavily on tight end T.J. Hockenson and running backs D’Andre Swift and Jamaal Williams in the pass game Sunday, even before Tyrell Williams’ injury.
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Williams was the only wide receiver to catch a pass in the first half, and quarterback Jared Goff’s 6.5 intended air yards per target ranked 23rd out of 30 qualifying quarterbacks through Sunday’s games.
With Williams out, the Lions finished Sunday with four healthy receivers: Kalif Raymond, Amon-Ra St. Brown, Quintez Cephus and Trinity Benson.
Hockenson, Swift and Jamaal Williams had eight catches each against the 49ers, while Raymond led all receivers with three catches for 50 yards.
“They did an admirable job of fighting their ass off because we really lost Tyrell there at the end of the game,” Campbell said. “We were down to four and those guys were kind of rotating, trying to help each other out. So they got high in reps, which is why we train the way we train, and they fought through it.
“Now, we made some plays, but we didn’t make enough to win the game.”
With the season a week old, the Lions’ depth already is being tested.
Okudah ruptured his left Achilles tendon in Sunday’s second half and will miss the rest of the season, and starting left tackle Taylor Decker is out through the end of the month after undergoing finger surgery.
The Lions play the defending NFC North champion Green Bay Packers in a battle of 0-1 teams at Lambeau Field next Monday night.