San Francisco 49ers defensive tackle Ricky Jean Francois has been preparing all week to start in place of All-Pro Justin Smith on the NFL's second-ranked defense.
The 49ers remain uncertain whether that will actually happen Sunday night in a NFC West showdown against the Seattle Seahawks.
Smith's availability is in question after he missed practice Friday because of an elbow injury for the third consecutive day, placing his streak of 185 consecutive starts in jeopardy.
The 49ers listed Smith as doubtful on an injury report they submitted to the NFL office Friday morning. He was upgraded to questionable later in the day, even though he didn't participate in the afternoon session.