SANTA CLARA -- Justin Smith's availability for the 49ers' playoff run remains uncertain, although the team clarified the extent of his left triceps injury Thursday.
Smith, the defensive line's mainstay, had a bone spur break loose from his left triceps, and it remains in his elbow. That triceps tendon remains partially attached, and the team is evaluating how Smith's arm responds to the injury suffered Dec. 16.
"You can't put into words what he means to this defense," linebacker Patrick Willis said. "More than being a captain, he's one guy who goes out and leads by example, plays with heart."
Smith hasn't played or practiced since getting hurt in the third quarter of the 49ers' win at New England. He was named Wednesday to his fourth straight Pro Bowl.
Upon Smith's departure, the 49ers have surrendered 73 points in their past six quarters -- 31 points to the Patriots in an eventual 41-34 win, and 42 points in Sunday's 42-13 loss at Seattle.
"We can't fill his shoes. Nobody can do that," Willis added. "But I know we can get it done."
The 49ers (10-4-1) can clinch their second straight NFC West title Sunday by beating the visiting Arizona Cardinals (5-10), or by virtue of the Seattle Seahawks (10-5) losing to the visiting St. Louis Rams (7-7-1). The 49ers also can clinch the NFC's No. 2 seed if they win and the Green Bay Packers (11-4) lose to the host Minnesota Vikings (9-6).
Smith hasn't been available for comment since after the win at New England. Teammates have spoken up, however, in defining Smith's massive value and the dire need to fill his void.
"Like I said to the guys before last game, we lost a strong guy in our defense, a guy that really demands a lot of attention," linebacker NaVorro Bowman said. "I called out everyone. Everyone needs to step up and turn their game up a notch.
Willis, one of the 49ers' four captains along with Smith, has taken on a more vocal leadership role with the media in recent weeks. Willis, too, has implored teammates to "take it up another notch," and that includes Ricky Jean Francois, Smith's replacement.
Willis, however, sympathized with Smith's plight and uncertain future: "I know it's killing him not to be out here with us. But he needs to do the right thing to get back, if not now, but for later in his career."
Smith played in 189 consecutive games and made 185 consecutive starts before being confined to the sideline during Sunday's debacle at Seattle. Although he hasn't practiced, he's continued to rehabilitate and do individual conditioning, coach Jim Harbaugh has said.
"He told me he's getting better each and every day," defensive coordinator Vic Fangio said.
The Sacramento Bee was first to report Thursday that Smith's injury is a partially torn triceps tendon rather than a simple elbow injury, as has been reported by the team.
Despite the poor results that have accompanied Smith's exit, Fangio isn't planning any sweeping changes to his normally successful schemes. The 49ers, after all, have five other Pro Bowl-bound defenders in Bowman, Willis, outside linebacker Aldon Smith and safeties Dashon Goldson and Donte Whitner.
Said Fangio: "We're too far along to change the system because one guy's out."
The Cardinals, despite losing 10 of their past 11, present the "ability to be explosive" with wide receiver Larry Fitzgerald, Fangio noted.
Two months ago, however, the 49ers routed the Cardinals 24-3. Justin Smith had only five tackles in that game, which matched his second-lowest output this season.
Smith's three sacks are the second-lowest total of his 12-year pro career, behind only the two sacks he compiled in his 2007 swan song with the Cincinnati Bengals. However, he has a team-high 73 quarterback pressures and 56 quarterback hits, and that presence has helped Aldon Smith compile a franchise-record 19½ sacks.
"He's one of the guys I look up to in this league," Willis said of Justin Smith. "I've been a fan of guys who give it their all. Hopefully we're able to get him back for the playoffs, but I also want to make sure he takes care of himself."