Why 49ers might have to adjust approach

San Francisco 49ers defensive end Justin Smith is expected to need two or three months to recover from triceps surgery scheduled for this week.

That gives Smith ample time to ready himself for the 2013 season.

2011-12 DL Snaps Counting Playoffs

One question: How many miles remain on the odometer for Smith? The Pro Bowl lineman had started 185 consecutive regular-season games before the injury. He has said he doesn't want to become just a situational player, but it's reasonable to wonder for how long a 33-year-old defensive lineman can play nearly every snap without breaking down physically.

Ray McDonald, Smith's teammate on the defensive line, was one of three NFL defensive linemen to play at least 90 percent of his team's defensive snaps during the 2012 regular season.

Smith would have pushed for a spot on the list if an arm injury hadn't forced him to miss time. Even with the injury, Smith ranks among the NFL's top four defensive linemen in total snaps logged over the past two seasons, counting playoffs. McDonald is also on the list.

The 49ers' defensive players have logged high miles over the past two seasons. The team relies upon a smaller number of defensive players than most teams in part because their inside linebackers, Patrick Willis and NaVorro Bowman, stay on the field for passing downs.

That is only part of the story.

With Smith and the 28-year-old McDonald playing so extensively for a team that has also played five postseason games over two seasons, the 49ers could clearly use a depth infusion up front on defense.