SANTA CLARA — Patrick Willis believes the San Francisco 49ers can still be a great defense even without All-Pro tackle Justin Smith.
The 49ers might have to spend the rest of this season finding out whether or not Willis, their All-Pro linebacker and defensive leader, is correct.
Smith is unlikely to play Sunday in the regular-season finale against Arizona because of a partially torn left triceps. The injury could force Smith to miss some or all of the postseason.
The San Francisco defense has been gouged for big yardage and points since Smith was injured early in the third quarter Dec. 16 at New England. But the NFL's second-ranked defense hopes to regroup and regain momentum for the playoffs against an Arizona team that ranks last in the league in total offense.
Smith, one of five San Francisco defenders selected to start for the NFC in the Pro Bowl, is expected to be on the sideline against the Cardinals.
"You can't really put into words what he means to this defense," Willis said Thursday. "We most certainly miss him and hopefully we'll get him back for the playoffs.
"But we have a great defense and I truly believe that. When you have what we have on our defense, we should be able to go out there and display that each time. Starting from this Sunday, we have to make sure we go out and do that on a consistent basis and play like the defense we know we're capable of playing like."
The 49ers haven't been the same on defense since losing Smith in the victory at New England.
San Francisco surrendered four consecutive touchdown drives after Smith left that game with the 49ers leading 31-3. Without Smith over most of the past six quarters, the 49ers have allowed 753 yards, 66 points and 48 first downs.
Much of that damage came last week in a 42-13 loss at Seattle, the worst defeat of coach Jim Harbaugh's two seasons with the 49ers. Without Smith, a first-team All-Pro and Pro Bowl starter last season, San Francisco's defense allowed season highs in both points scored and rushing yards allowed.