All-Pro outside linebacker Aldon Smith figures to see a lot of playing time Sunday against the Carolina Panthers in his return after a five-game absence. Smith routinely played every defensive snap for the 49ers before taking a voluntary leave of absence Sept. 23 to seek treatment for substance abuse. Will he play every every snap in his return to action at Candlestick Park? “After a six-week layoff, he might not be ready, conditioning-wise,” 49ers defensive coordinator Vic Fangio said. “Every game takes on its own personality. How many plays you’re playing. How many plays you’re playing in a row. How many plays you’re playing in different packages. It remains a fluid situation. “I’m sure he’ll play some. We’re monitoring the situation. If nothing happens between now and then, I’m anticipating that. But nothing’s been etched in stone, yet.” Smith returned to the practice field on Monday. He was a full participant in on-field work on Wednesday when the 49ers had their one padded practice of the week.