CHARLOTTE – Left tackle Matt Kalil was not at practice for the second consecutive day, and now we know why.

Head coach Ron Rivera said Kalil has been dealing with knee soreness since training camp.

"We're going to get it evaluated further," Rivera said. "It just all kind of came to a head. We'll wait to see what the doctor says."

Rivera is hoping Kalil's situation is just precautionary as the start of the regular season fast approaches. Down in Spartanburg a few weeks ago, Rivera was happy to see Kalil's strength and quickness were back, adding that he expected Kalil to "improve and be better for us this year."

"He's practiced well," Rivera said. "He struggled a little bit the other day (against Miami) because of it. But for the most part, hopefully it's just one of those things where it's a little something here or there and he'll be ready to roll once we get ready for the season."

With Kalil sidelined, Taylor Moton moved from right to left tackle and Jeremiah Sirles stepped in at right tackle.

The Panthers are already without starting right tackle Daryl Williams and starting left guard Amini Silatolu, both of whom suffered knee injuries during camp. Rivera said rehab is going well for both guys but that there's not yet a timetable for their return.

"Absolutely concerned," Rivera said. "You've got three potential starters right now that are missing time. It's going to be tough. But as coaches, we have to continue to do the best job we can to make sure everybody gets prepared."