SANTA CLARA Justin Smith's streak of 185 starts is in jeopardy.
The 49ers defensive end missed his third straight practice Friday after leaving Sunday's game in New England with what the team said was an elbow injury.
The 49ers listed Smith as questionable on their injury report Friday; an earlier report the team sent to the NFL, however, listed him as doubtful.
A questionable designation means there is a 50 percent possibility of playing; doubtful means there is just a 25 percent chance.
Earlier in the week, 49ers coach Jim Harbaugh sounded optimistic that Smith, a three-time Pro Bowl player, would be able to practice. Smith did not practice during the week, but Harbaugh said Friday that Smith had made good progress in "rehab, strengthening, conditioning."
Smith, 33, is at a stage in his career where he doesn't need to practice during the week to be able to play in the game. Whether he's on the field in Seattle may come down to how he feels a couple of hours before kickoff.
Smith, one of the toughest players in the league, tried unsuccessfully to return to Sunday's game against the Patriots. That attempt came in the fourth quarter when the 49ers were losing both momentum and their big lead and desperately needed one of their mainstays to help regain momentum.
Backup Ricky Jean Francois said he expected to start at Smith's right defensive end spot against Seattle.
"Just another start," said Jean Francois. "I ain't going to be sitting on the bench, not being able to get in the game. So this week the preparation was a little bit different more film, more details on their offense. Usually I'm on the sideline."
Jean Francois, scheduled to be a free agent in March, stepped in for Smith on Sunday and had a key sack of Tom Brady late in the game.
"He played well," defensive coordinator Vic Fangio said. " He had a big sack on third down, which forced them to punt."
The team also could activate nose tackle Ian Williams for the first time this season, which would allow Isaac Sopoaga to play defensive end in an emergency. Will Tukuafu, recovering from a concussion this week, also is a backup at defensive end and nose tackle.
Smith's consecutive starts streak is the longest for an active defensive lineman and the third-longest of any player behind Tampa Bay cornerback Ronde Barber (213) and Washington inside linebacker London Fletcher (193).
"It's super impressive," left offensive tackle Joe Staley said of Smith's streak. "Not only to play on the line but to play the way he does the physicality and he plays every single play."
Fatigue factor The 49ers' defenders are heading into what promises to be a physical game in Seattle after playing the equivalent of a game and a half in New England.
In a normal game, an every-down defensive player can expect to be in on about 55 snaps. The 49ers' defense was on the field for 92 plays Sunday, 60 in the second half.
"Well, there's no doubt they ended that game a little more tired than a normal game," Fangio said. " So they were more tired than usual, particularly when you have that many passes thrown against you. Pass rush is very taxing on the big guys. But I feel like we're back to normal now."
Et cetera The 49ers promoted seventh-round pick Cam Johnson, an outside linebacker, from the practice squad to the active roster.
Outside linebacker Clark Haggans (shoulder) also missed practice this week and is listed as questionable.
Wide receiver Mario Manningham (shoulder) is questionable. He was limited in practice throughout the week.