The 49ers went into halftime down 16-10 with two prominent players on the bench -- outside linebacker Ahmad Brooks and quarterback Colin Kaepernick.
Brooks is the oldest and most experienced member of the 49ers defense. But he was goaded into an embarrassing penalty in the second quarter by Rams center Tim Barnes and struck Barnes in the facemask in plain view of the officials.
That turned a third-and-12 scenario for the Rams into a first down, and they scored a field goal on the drive.
As has been the case at various points over the last two seasons, Brooks was sent to the bench where he remained for the rest of the first half.
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He was benched last year after arguing about playing time with then defensive line coach Jim Tomsula during a game against the Giants. He missed another game that season after being late for a team meeting.
Earlier this year in Chicago, Brooks threw his helmet on the 49ers sideline, which earned him a brief benching from Tomsula. He later re-entered that game.
Brooks and offensive lineman Erik Pears are tied for the team lead in penalties this season. Each has been flagged 11 times. Seven of Brooks' penalties have been defensive offsides or neutral-zone infractions.
Kaepernick, meanwhile, is on the sideline for the first time since he had surgery on his left, non-throwing shoulder last month.
Both he and Brooks are under contract for next season. However, Kaepernick is due to make $14 million in 2016 if he is still on the roster beyond April 1 and the expectation at this point is that the team will part ways with him before then.
Brooks, meanwhile, was replaced with rookie Eli Harold when he was benched. Harold is being eyed as his long-term replacement as well.