"My gut says he'll play," Rivera said of Smith, the team's all-time leading receiver.
Smith sprained his posterior cruciate ligament in a Week 16 win over New Orleans and has not played since for the Panthers (12-4).
Smith, who has been coy about the injury all week and pulled some bizarre numbers out of thin air to describe his health, looked up at his jersey number and joked there's an "89 percent" chance he'll play against the 49ers.
Smith had estimated Wednesday he was 71 percent and then downgraded himself to 57 percent on Thursday before finally saying that, "Honestly, I just randomly pick numbers."
Smith grinned and said that he settled on 57 percent after winning a rock-paper-scissors matchup with injured offensive lineman Jeff Byers on Thursday.
Byers wanted him to pick 62 percent.
"I won," Smith said. "See, I have kids and he doesn't. I'm well experienced for rock-paper-scissors."
NFL: Two players violated concussion protocol
Two players violated league concussion protocol during last weekend's wild-card games, according to a letter sent by the NFL's head, neck and spine committee chairmen to all team doctors and trainers.
In a document obtained by The Associated Press, Drs. Hunt Batjer and Richard Ellenbogen said one player re-entered the game and another refused to leave the sideline.
The doctors did not identify the players, but one was Green Bay tackle David Bakhtiari, who went into the game for an extra-point try despite being examined for a concussion and not cleared. The other player was Saints cornerback Keenan Lewis, who remained on the sideline but did not get back on the field.
"On two occasions last weekend, and contrary to the advice of the team medical staffs, players who had been diagnosed with a concussion and therefore declared ineligible for play nonetheless refused to leave the sidelines as required by league concussion protocols," the letter said. "In one case, the player went back onto the field for one play before being removed from the game."
The doctors found "no fault" in how the team medical staffs conducted themselves.
Around the league
Bengals • Hue Jackson was introduced as the successor to Jay Gruden, who is now coach of Washington after three years as Cincinnati's offensive coordinator.
Dolphins • Former Washington offensive coordinator Kyle Shanahan and Eagles quarterbacks coach Bill Lazor have interviewed for Miami's offensive coordinator job.
Texans • Tackle Duane Brown has been added the Pro Bowl roster. The NFL announced that the Texans' sixth-year veteran offensive lineman will replace Philadelphia Eagles tackle Jason Peters in the Jan. 26 game in Honolulu.
Colts • Receiver Darrius Heyward-Bey will not play in Saturday's playoff game at New England. Heyward-Bey did not practice all week because of a hamstring injury.
Bills • Buffalo re-signed veteran punter Brian Moorman to a one-year contract extension that locks him up through next season.