The San Francisco 49ers could have their quarterback back in the starting lineup Sunday against the Buffalo Bills. Brock Purdy was spotted throwing during Friday’s practice while Brandon Allen was wearing a scout team jersey. That suggests Purdy will be available after missing Week 12’s game against the Green Bay Packers.

Purdy is officially questionable for Sunday’s game, although Shanahan expects him to play. However, Purdy is unlikely to have all five starters along the offensive line. Shanahan ruled out the left side. Neither left tackle Trent Williams (ankle) nor left guard Aaron Banks (concussion) were spotted during Friday’s practice.

At this point, Banks may be addition by subtraction. Sports Info Solutions credited Banks with three blown blocks against the Packers. On the season, he leads the team in blown blocks. Spencer Burford and Ben Bartch will be active in Banks’s place if he doesn’t clear the concussion protocol. Burford, who has filled in for Banks this season, figures to take over Banks in the starting lineup.

Jaylon Moore is in line for his second straight start without Williams. Moore doesn’t need to be the All-Pro that Williams is for the offense to function. He just has to avoid the “lookout” blocks that cause turnovers.

Cornerback Deommodore Lenoir is out with a knee injury, as is Nick Bosa (hip/oblique) and Jordan Eliott (concussion). Lenoir’s absence could mean Renardo Green takes over in the slot, although Isaac Yiadom has played there this season as well.

Sam Okayinonu started and played more snaps than Leonard Floyd last week, but the same number as Yetur Gross Matos at 45. Those two will likely split reps again as they fill in for Bosa.

Elliott played 25 snaps against the Packers. Evan Anderson played 36 and had four tackles. Maliek Collins played 46 snaps, while Kalia Davis played 29. Sunday night may require more from Robert Beal Jr., who played a season-high 21 snaps against Green Bay.

Linebacker Dre Greenlaw won’t play. Kyle Shanahan said there hasn’t been a decision on when we’ll see Greenlaw, but the schedule sets up for his season debut in Week 15 against the Los Angeles Rams. That’s a quick turnaround after Week 14’s matchup against the Chicago Bears.