The winless 49ers might get a glimpse into the future of their offensive line on Sunday against the Cardinals.

Promising third-year tackle Trent Brown is expected to the start at left tackle in place of Joe Staley, who’s expected to miss the next two games after suffering an orbital fracture beneath his right eye Sunday in Philadelphia.

Brown, 24, will be eligible for a contract extension after the season, and might wind up being the long-term replacement for Staley, 33, whenever the five-time Pro-Bowler ends up leaving the team.

There’s been no indication Staley is on the outs or that his production has dropped enough to warrant San Francisco trying to move on as it continues the rebuilding effort. Staley remains one of the team’s most valuable players given his relative affordability beyond this season.

He’s due to count for $7.7 million against the salary cap over the next two years while 22 offensive linemen throughout the league average eight figures per season, according to Overthecap.com.

But at some point, Brown may move to left tackle on a permanent basis. He made his first career start there Week 16 last season against the Rams and allowed just one pressure in 48 passing plays, according to Pro Football Focus.

“It’s not really difficult,” Brown said of switching from right tackle to left. “I’ve been doing that since I’ve been here.”

The transition was much more difficult for Staley early in his career. He played right tackle his rookie season before transitioning to the left side, where he’s remained the last decade.

“It’s really hard. It’s difficult. He’s got a big challenge, just because of the footwork and the mindset,” Staley said. “It’s different and it’s hard. It’s not just tackle is tackle. Right and left is a lot different in your brain.

“I remember just moving in college, even, from right to left, took me like two or three weeks. I was always flipping the plays in my head. I was all over the place. I thought he’s done a really good job. He’s a really natural athlete.”

The 49ers may have right guard Brandon Fusco back after missing practice Wednesday and Thursday for a second straight week. He’s been dealing with a biceps injury and wasn’t listed on the final status report Friday.

San Francisco is expected to add defensive lineman Ronald Blair from injured reserve after placing receiver Pierre Garçon and offensive lineman Garry Gilliam on injured reserve with neck and knee injuries, respectively.

The 49ers will add undrafted rookie Darrell Williams Jr. to to the active roster from the practice squad, according to the Sacramento Bee. That could leave San Francisco with three reserve linemen available for Sunday if Zane Beadles starts at right tackle: Erik Magnuson, newcomer Bryce Harris and Williams.