Gallery and second-year offensive lineman Paul McQuistan both split time at right tackle in practice Wednesday, but Raiders coach Lane Kiffin wouldn't say yet which way he's leaning.
"We're going to look at a couple things," Kiffin said. "Paul could be out there. Robert could be out there. As far as the plan for Sunday, it could be either of those."
McQuistan was drafted as a guard but has played twice this season in relief of Green at right tackle. He struggled both times, picking up a pair of penalties in the 29-22 loss to Minnesota.
Gallery, who played both tackle positions during his first three seasons in the NFL, was moved to left guard in the offseason by line coach Tom Cable and helped pave the way for the league's top-ranked rushing team through the first month of the regular season. But he and the rest of the Raiders offensive line have struggled in recent weeks while the team has dropped six straight games.
If Gallery were to be moved, the Raiders would then use either McQuistan or Chris Morris at left guard.
"Cornell's down and they're going to have to make a change," Gallery said. "I haven't done it in a year or so, but they're going to do what's best for this football team. People get hurt in this league and changes have to be made. Somebody's got to be able to play."
The Raiders signed offensive lineman Seth Wand to take Green's spot on the roster. Wand, a third-round pick of Houston in 2003, started 16 games in 2004 but was released by the Texans two years later. He signed with Tennessee late in 2006 and played exclusively on special teams.
Oakland also has rookie Mario Henderson on its roster but the third-round draft pick has yet to be active for a game this season.