SEATTLE -- The 49ers' defense has surrendered nine touchdowns in the six quarters of play without All-Pro defensive tackle Justin Smith, who missed Sunday's game with a left elbow injury.
Smith is not expected to return for the 49ers' regular-season finale against the Arizona Cardinals, and coach Jim Harbaugh did not sound certain Smith will be available for the playoffs, either.
"I don't know for sure," Harbaugh said following the 49ers' 42-13 loss to the Seattle Seahawks on Sunday night.
Ricky Jean Francois, who started at right defensive tackle in Smith's place, said he is mentally preparing himself for the possibility that Smith will not be back.
"I know he's a big part of our defense," Jean Francois said. "All I can be is Ricky Jean Francois. Would love for Justin to come back, but if he doesn't I'm here to pick up the slack or pick up that space right there."
The 49ers have been a different defense with Smith out of action. The team surrendered 28 points in the second half after Smith left the field due to his injury early in the third quarter of the 49ers' 41-34 win at the New England Patriots last week.
On Sunday, Seahawks running back Marshawn Lynch rushed for 111 yards and a touchdown, and quarterback Russell Wilson threw four touchdown passes.
"I think it's a big deal," 49ers safety Donte Whitner said of Smith's absence. "I think not having Justin is a huge deal. Not only what he does against the run but what he does against the pass. How he helps Aldon (Smith) out there, eating up two guys allowing him to go one-on-one. He's a huge part of this defense.
"He has an injury and we don't have him right now, so all that we can do is for the guys that are in there to back them up and everyone needs to pick up their game and take it to another level. We can't make excuses. We understand we lost this football game. It was an ugly football game, but professional athletes are men of high character. We will bounce back next week."
Aldon Smith has not recorded a sack in the past two games. He was not credited with any quarterback pressures against the Seahawks, who appeared to target Jean Francois in the run game. Lynch's 24-yard touchdown run in the first quarter was right at Jean Francois.
Offensively, the 49ers have injury concerns, too.
Receiver Mario Manningham sustained ligament damage to his left knee while fumbling in the third quarter. He left the 49ers' locker room on crutches. It's uncertain how long Manningham will be out of action.
Tight end Vernon Davis sustained a concussion in the first quarter on a hit from Seahawks safety Kam Chancellor, who was penalized on the play. Davis did not return to action. He will have an opportunity to clear the necessary tests to play in the regular-season finale against the Arizona Cardinals.
"Vernon told me he had a mild concussion," Harbaugh said.