Guard Darnell Stapleton, who has been bothered by an undisclosed left knee injury, will have arthroscopic surgery Friday morning and will be sidelined for an indefinite period.

Steelers coach Mike Tomlin would not say how long Stapleton, who is also the backup center, will be sidelined, but such procedures are usually two to four weeks.

"We will have more information after [the surgery] is completed," Tomlin said.

Stapleton has missed the past four days of practice and has been replaced by backup tackle Trai Essex, who could remain in that position even when Stapleton returns.