Steelers offensive lineman Darnell Stapleton will have arthroscopic surgery on Friday morning on his left knee. Head coach Mike Tomlin would not give a definite time frame on how long Stapleton will be sidelined. Stapleton, who has missed the past four days of practice, had been working as the backup center in the absence of Justin Hartwig who is recovering from a toe injury. Trai Essex will continue to work at the starting right guard position.
