LAkE FOREST, Ill. — The Chicago Bears have another potential problem on their offense line.

Left tackle Jermon Bushrod has a knee injury suffered in practice that kept him from practicing Wednesday and Thursday. He is day to day, according to coach Marc Trestman. Bushrod hasn’t missed a start as a Bear or since 2009 when he was with the New Orleans Saints.

Trestman would not say how the injury occurred and only that Bushrod “went to the ground.” He also called it “accidental.”

Without Bushrod, the Bears would have inexperience blocking quarterback Jay Cutler’s blind side, at best. They have not had left guard Matt Slauson and center Roberto Garza because of ankle sprains the last three games. Both practiced on a limited basis Wednesday and Thursday, and their availability remains uncertain for Sunday’s game at Charlotte with the Panthers.

If Slauson can play, then backup guard Michael Ola could be shifted to left tackle. Ola, who has started at left guard the last three games, played left tackle briefly in preseason and also right tackle. Also, the Bears have tackle Charles Leno Jr., a rookie seventh-round draft pick out of Boise State.

Asked who would go to the spot and who has practiced there with Bushrod out, Trestman merely said: “I think that the only way I can answer that is we are working through this problem by moving people around.”

Bushrod was signed by the Bears for $44 million last year. Pro Football Focus reported he allowed four sacks last season.

“He quietly does his job each and every week,” Cutler said. “Most teams you go against have a defensive end or somebody who specializes to get to the passer and Bushy over there just takes care of guys. You don’t have to worry about it. You know the left side is locked up and let’s worry about what’s inside.”