James Harrison had returned to practice Tuesday for the Pittsburgh Steelers after a knee injury sidelined him for the season's first three games, but he did not practice Wednesday after suffering what his his agent deems as "a setback."

After arthroscopic knee surgery on Aug. 15, Harrison missed all of the Steelers' practices until Tuesday when he participated in his first full practice since the surgery. It didn't go well: Harrison had hoped to participate in practice again Wednesday, but instead left the Steelers' training facility with the knee bothering him.

It's unclear where Harrison and the Steelers go from here. The five-time Pro Bowl linebacker was supposed to shake off the rust during the bye week, with the goal of playing Oct. 7 against the Philadelphia Eagles. His goal is still to play in that game, but it grows less likely with each day he can't practice.

On the other hand, Troy Polamalu participated in both practices after a calf injury sidelined him for the Steelers' games against the New York Jets and Oakland Raiders. He is expected to return next weekend.

This story was originally published on SBNation.com.