Stacy didn't practice Wednesday but returned Thursday full-time and was moving around well before reverting to practicing on a limited basis Friday. At the time, it appeared the Rams were just taking proper precautions to get Stacy's ankle back to as close to full strength as possible in time for Sunday's game.
It's no surprise that Stacy is ready to go. Based on how he was moving around, I'd expect him to get a fairly large workload Sunday barring some sort of re-injury.
The backup situation is a bit more tenuous. Daryl Richardson's foot injury made him questionable and he didn't do much in practice all week. Benny Cunningham appears poised to return this week after missing the past two weeks with an ankle injury. He was listed as questionable also but participated fully in practice all week.