SANTA CLARA, Calif. -- 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 defence.
The 49ers remain uncertain whether that will actually happen Sunday night in their NFC West showdown against the Seattle Seahawks.
Smith's availability is in question after he missed practice Friday for the third consecutive day because of an elbow injury, 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 team's afternoon session.
Coach Jim Harbaugh, who indicated earlier in the week he expected Smith to play against the Seahawks, didn't elaborate on Smith's status other than to say "he's done quite a bit, rehab, strengthening, conditioning."
Smith has the third-longest active starting streak in the NFL behind Tampa Bay's Ronde Barber (213 consecutive starts) and Washington's London Fletcher (197). A 12-year veteran, Smith hasn't missed a start since early in his rookie season with Cincinnati.
Jean Francois is ready if Smith misses this one.
"Just another start," Jean Francois said. "I'm not going to be sitting on the bench, not able to get in the game. So the preparation this week was a little different. I'll see a lot more action."
Jean Francois ended up playing 48 of San Francisco's 92 defensive plays last week in a 41-34 victory over New England. Smith left that game early in the third quarter, got his elbow taped in the locker room and returned to the San Francisco sideline. But he never went back in the game.
The Patriots scored 28 straight points with Smith on the sideline to erase a 31-3 San Francisco lead, rolling to touchdowns on consecutive drives of 73, 86, 66 and 92 yards.
But Jean Francois and left tackle Ray McDonald both came up with big plays as the 49ers stopped New England on its next two offensive series late in the fourth quarter after San Francisco regained the lead.
Jean Francois and McDonald had back-to-back sacks of quarterback Tom Brady to halt New England's momentum on the first of those series. Jean Francois beat New England left tackle Nate Solder on third down for his second career sack, forcing New England to punt for the first time since the second quarter.
"Ricky played well," 49ers defensive co-ordinator Vic Fangio said. "He had a critical sack there when we finally got them stopped, which were critical drives. He's a well-rounded player that can play both the banging game and he's got a little bit of athleticism, too. He's the one guy on our front that can play all three spots and nothing will change with him in there."
Jean Francois has started at both nose tackle and left tackle in San Francisco's 3-4 defensive scheme since being drafted by the 49ers in 2009. Smith's presence on the right side hasn't given him many opportunities there.
Jean Francois has become a regular part of San Francisco's defensive line rotation that includes McDonald and starting nose tackle Isaac Sopoaga. His 34 tackles this season already are a career high, and Jean Francois had 11 tackles over a two-game stretch in September which included one start in place of an injured Sopoaga.
"I'm just trying to show my coaches that I'm someone you can trust when the times get really tough," Jean Francois said. "You can put me in and the ball will never drop. That's the biggest thing, just making sure the ball keeps rolling whether it's Ray out or Justin out."
Smith is a key cog in San Francisco's third-ranked rushing defence that will collide Sunday with Seattle's third-ranked rushing offence. Smith's 130 tackles rank third on the team behind All-Pro linebackers NaVorro Bowman and Patrick Willis.
But if Smith's not there, the 49ers are confident Jean Francois can hold the line.
"Ricky's a very good player who could start for a lot of football teams in the NFL," said 49ers Pro Bowl offensive tackle Joe Staley, who lines up against both Smith and Jean Francois in practice. "He fits the scheme really well and he knows exactly what he's doing. Obviously, Justin is Justin Smith, one of the best players in the NFL. But Ricky does a terrific job going in there, and if he's in there we expect him to do great things for us."