ST. LOUIS -- Reggie Bush was carted off the field in the first quarter after he slipped on the concrete surface behind the 49ers bench and slid into a wall, injuring his knee. Another running back, rookie Mike Davis, has been ruled out with a hand injury.
That leaves Kendall Gaskins, who before Saturday was on the practice squad, as the 49ers’ only healthy runner. The Rams lead 20-6 at halftime.
Bush was returning a punt from one side of the field to the other when he ran out of bound at a high rate and was given a shove by a Rams defender. The Edward Jones Dome’s turf ends 15 or so yards out of bounds and the surface turns to concrete.
Bush was earmarked for a bigger-than-usual role Sunday. Without Carlos Hyde (foot), he started the game at running back. He also was the 49ers’ punt returner after the team waived Jarryd Hayne Saturday. The 49ers have 18 yards on the ground at the half; the Rams have 108 yards.
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Bruce Ellington returned punts after Bush left the game. Davis finished with four yards on 10 carries; Gaskins has run once for minus-2 yards.
Following Bush’s injury, the 49ers suffered a safety when Davis was tackled in the end zone.
Several 49ers have gone down with injuries.
Special teams ace L.J. McCray injured his knee while covering a punt. He has not returned. Nor has tight end Garrett Celek, who is being evaluated for a possible concussion.
Cornerback Kenneth Acker and defensive lineman Quinton Dial each had to be helped off the field during the Rams' last touchdown drive; neither appears seriously hurt and Acker returned to the game.
Another cornerback, Keith Acker, left the game with an ankle injury.