Gore, whose contract is up at the end of the season, is going through the NFL's mandated concussion protocol after leaving Sunday's loss to the Seattle Seahawks with a head injury.
The "heart and soul" of the 49ers, as offensive coordinator Greg Roman called Gore Thursday, returned to practice after not practicing earlier in the week. He was wearing a blue non-contact jersey, but said he feels good and the decision of whether or not to play is up to the team's medical staff and his progress through the protocol.
Gore must pass a contact test before being cleared to play Saturday against the San Diego Chargers.
Head coach Jim Harbaugh Thursday said he expects newly-acquired running back Phillip Tanner to be dressed and active for Saturday's game. Rookie running back Carlos Hyde is not expected to play after sustaining an ankle injury in the third quarter last week. He has not practiced since the injury.
Running back Alfonso Smith will figure into the game plan whether or not Gore plays Saturday. If Gore is held out, then Smith is likely to receive the majority of the carries after filling in during the second half of Sunday's loss in Seattle, where he ran for six yards on four carries. Tanner would also be worked in.
--Rookie center Marcus Martin, who missed last week's game with a knee injury suffered in the loss to the Oakland Raiders, is questionable to play Saturday. "He’s done some things in practice pretty well. And, I think Marcus’ performance, he has earned the right to be the starter there,” Roman said.
Roman wasn't as complimentary about Martin's replacement Joe Looney, who made his first career start at center Sunday against the Seahawks in noisy CenturyLink Field. Looney was Pro Football Focus' lowest-graded 49ers lineman for the day. San Francisco allowed six sacks to Seattle's top-ranked pass defense.
“He had a tough game. There were some things there that fundamentally he could have done better," Roman said. "You know, first start as a center, in that environment, against that crew which is pretty good, that’s tough duty. But, I think he could have played better.”
--Receiver Stevie Johnson has not practiced this week, and appears unlikely to play Saturday with a lingering knee injury suffered Oct. 19 against the Denver Broncos, according to the San Francisco Chronicle.
That means San Francisco will have an opportunity to look at their younger receivers Bruce Ellington and Quinton Patton, who have played sparingly on offense this season. Patton made his season debut just two weeks ago against the Raiders after being inactive for the previous 12 games. The second-year wideout is still looking to make his first catch of 2014.
Ellington, who missed time with an ankle injury before returning in Oakland, has played just 79 snaps on offense this season. And given the uncertainty surrounding Michael Crabtree's return next season, the 49ers might be wise to see what they have with Ellington by giving him a prolonged look over their final two games.
"I think those guys are doing a great job in practice," Roman said. "Bruce coming off his situation was a guy we didn’t want to overload with his special teams duties. But, I feel like he settled nicely back into that."
Crabtree is a pending free agent likely to demand more than the 49ers are willing to offer considering his level of production this season. His troubled injury history will also be considered. That includes last year's torn Achilles and foot injuries that have popped up at various times throughout his career, including earlier this season.
Ellington owns the 49ers only fourth-quarter touchdown this season. He connected with backup quarterback Blaine Gabbert on 20-yard score in the blowout loss to the Broncos.
Thursday's 49ers injury report
Did not practice:
LB Chris Borland (ankle), CB Tramaine Brock (hamstring), RB Carlos Hyde (ankle), WR Steve Johnson (knee), T Jonathan Martin (illness)
LB Ahmad Brooks (thumb), WR Michael Crabtree (knee), T Anthony Davis (concussion), RB Frank Gore (concussion), S Raymond Ventrone (groin), LB Michael Wilhoite (hip)
CB Perrish Cox (ankle), CB Chris Culliver (knee), DT Quinton Dial (knee), DE Tony Jerod-Eddie (foot), C Marcus Martin (knee), LS Kyle Nelson (back), DE Justin Smith (back)