I don't have the specifics from the team yet, but Barrows just posted that Mike Singletary announced Frank Gore would be a game-time decision. It's a link, but obviously worth a little more face time than most links.
According to Barrows:
Gore will not practice today and Singletary said that DeShaun Foster will get the bulk of the practice repetitions this week. If Thomas Clayton is elevated to the active roster, it will be later this week, perhaps Saturday.
Apparently it's "inside sprain" of the left ankle and NOT a high ankle sprain. I remain convinced Gore will play this Sunday. Consider the facts: it's his hometown and he's so close to the third consecutive 1,000 yard season (which no 49er RB has accomplished). If Gore ended up inactive on Sunday it'd have to take some pretty strong action from Singletary.
Also, according to Barrows, Nate Clements is likely to be probable this week after having the pin removed from his finger. Josh Morgan will see a full practice while Arnaz Battle apparently aggravated his foot sprain and won't practice today. More to come on all these injuries.