CHARLOTTE, N.C. -- Panthers coach Ron Rivera said wide receiver Steve Smith and linebacker Jon Beason are expected to play in the team's Sept. 9 regular season opener against Tampa Bay after both returned to practice Sunday.

However, Rivera isn't sure about running back Jonathan Stewart, who remains out with a sprained ankle.

With Smith and Beason back, Stewart is the biggest concern as the Panthers enter the season opener. Although the Panthers have plenty of depth at running back, Stewart gives the team a big bruising back and someone to spell starter DeAngelo Williams.

"We'll see," Rivera said when asked if Stewart will be ready for the Bucs. "We don't know until he gets out here and starts running around."

Stewart spent Sunday running on the treadmill inside the stadium, Rivera said.

Smith missed the last two preseason games with what the team described as a left foot infection. However, Rivera said Smith looked just fine in his first practice and didn't miss a beat in his first work in two weeks.

"Right away he went back into his normal practice mode, which is 100 percent," Rivera said. "It was good to see him back on the football field for sure."

Smith said he doesn't know what caused the infection.

Smith, the team's all-time leader in yards receiving and touchdowns, said the foot got infected underneath the skin. It began to swell and things snowballed from there.

"It's one of those things that happened and I'm not really sure why," Smith said. "So I had to get meds and IVs. It was scary not being able to walk and having to get medicine every day. There was a little bit of nervousness."

Smith said he didn't need surgery.

Beason didn't participate in any of the preseason games after injuring his hamstring early in training camp. He split reps in practice Sunday with Jason Phillips, who has been filling in at middle linebacker in his absence.

Beason said the biggest thing now is not pushing the hamstring too fast.

"Coaches are limiting me in practice, but all in all it was a great day," Beason said. "As of today I feel good."

Beason also missed the entire preseason last summer with tendinitis in the lower left leg and then went out and tore the Achilles in that same leg in the season opener against Arizona, thus ending his season.

He said he's not worried about something similar happening this year.

"It's a different injury," Beason said. "When you deal with tendinitis you can only treat it and it goes away on its own. But as far as hamstrings are concerned it's more a strength thing. If there's too much fatigue that's where you begin to get into trouble."

Smith and Beason were captains last year and are considered key cogs for the Panthers.

Smith has played in five Pro Bowls and Beason three.