Who will be 49ers running backs Saturday?

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The 49ers’ top two running backs Saturday night: Alfonso Smith and Phillip Tanner?

That remains a possibility after Frank Gore (concussion) and Carlos Hyde (ankle) missed practice Wednesday because of injuries that forced them to leave a 17-7 loss at Seattle on Sunday. Gore said he has felt “normal” since Sunday night, but he needs to clear the NFL’s concussion protocol to play against the visiting Chargers in what could be his penultimate game with the 49ers.

On Wednesday, the 49ers signed Tanner to shore up their banged-up backfield. Tanner, 26, entered the NFL with the Cowboys as an undrafted free agent in 2011 and had 149 yards on 56 carries (2.7 yards a carry) and two touchdowns in three seasons. Tanner was last with the Bills, but he was inactive for three games before Buffalo released him Nov. 20.

On Sunday, the 49ers’ only remaining running back was Smith, a five-year veteran who hadn’t played an offensive snap since he was signed

Nov. 11. Smith, 27, had

San Francisco 49ers running back Alfonso Smith (38) warms up before an NFL football game against the Seattle Seahawks in Santa Clara, Calif., Thursday, Nov. 27, 2014. (AP Photo/Tony Avelar) San Francisco 49ers running back Alfonso Smith (38) warms up before an NFL football game against the Seattle Seahawks in Santa Clara, Calif., Thursday, Nov. 27, 2014. (AP Photo/Tony Avelar) Photo: Tony Avelar, Associated Press Photo: Tony Avelar, Associated Press Image 1 of / 1 Caption Close Who will be 49ers running backs Saturday? 1 / 1 Back to Gallery

6 yards on four carries and inspired this response from Seattle defensive end Michael Bennett: “I don’t even know who No. 38 is.”

Johnson sidelined: Wide receiver Stevie Johnson said he has been dealing this season with a knee injury he sustained in a loss at Denver on Oct. 19. Johnson first appeared on the injury report Dec. 3 and he missed his first game Sunday.

Johnson, who hasn’t practiced this week, has 10 catches for 120 yards and no touchdowns in the six games he has played since the loss to the Broncos. He had 25 catches for 315 yards and three touchdowns in his first seven games.

Other injury news: Outside linebacker Ahmad Brooks (thumb), linebacker Michael Wilhoite (hip) and wide receiver Michael Crabtree (knee) were among nine players who didn’t practice.