"I will be all right," Smith said after Friday's practice. "I should be OK."
Panthers coach Ron Rivera listed Smith, running back Jonathan Stewart and defensive tackle Colin Cole as questionable — or 50 percent — for Sunday on the team's injury report.
"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."
Smith said Thursday that cutting was an issue for him.
He said he ran about five routes in practice Friday before it started raining hard. He said it was hard to judge if he'd improved much.
"I didn't want to aggravate it," Smith said.
The 34-year-old Smith has been a durable player for the Panthers over his 13 seasons, never missing more than two games in a year except for 2004 when he broke his leg in the season opener.
Smith has played in 182 games, starting 161.
"The unfortunate part about getting injured, whether you're an important piece or a non-important piece, life goes on," Smith said. "Game plans have to be made. Alterations have to be made just in case you're not able to go. That's the bad part about injuries. The real world still goes on."