Aldon Smith expected to play

SANTA CLARA, Calif. -- It appears Aldon Smith will play for the San Francisco 49ers on Sunday against the Carolina Panthers.

It will be the first game Smith, a premier pass-rusher, is back with San Francisco after he spent five weeks in a treatment center.

"I'm sure he will play some," San Francisco defensive coordinator Vic Fangio said Thursday. "Not sure how much."

Fangio said Smith was predictably looked a bit rusty in practice this week, but he attributed that to being away from the game for six weeks. Fangio said he expects Smith to knock off the rust quickly.

Smith participated in his first full practice Wednesday since he left the club Sept. 23. Smith said Tuesday the idea of playing Sunday was crossing his mind. On Wednesday, 49ers coach Jim Harbaugh said it would be a football decision. Harbaugh did say Smith looked like he is ready.

The 49ers are 5-0 without Smith. However, they have had just five sacks in the past four games. They had seven sacks when Smith played. He accounted for 4.5 of those. The 49ers will need all the extra pass rush they can get Sunday against visiting Carolina. According to ESPN Stats & Information, the 49ers use a traditional four-man pass rush at the second-highest rate in the NFL.

However, Carolina quarterback Cam Newton has completed an NFL-high 77.9 percent of his passes against such pressure since Week 6. Thus, using Smith in a blitzing situation could help. Smith has 38 sacks since entering the NFL in 2011. It is the second-most in the league in that time span.