The question of depth among the Pittsburgh Steelers this preseason became a bit murkier when it was reported LB Stevenson Sylvester suffered a torn medial collateral ligament in his knee, and will miss at least three to four weeks.

Sylvester was being looked upon to provide depth at both inside and outside linebacker, two positions reeling from retirement and injuries. OLBs James Harrison and Jason Worilds have been out through essentially all activity this preseason, and rookie LB Sean Spence is now likely the main back-up to either ILB, Larry Foote or Lawrence Timmons.

LB Brandon Johnson will likely see more time outside, as will Spence on the inside. With little time to prepare for a regular season that starts three weeks from today, the Steelers will need both players as well as other reserves like OLB Chris Carter - the likely starter in the event Harrison cannot play in the season opener - to be ready to play.

The news comes in wake of the Steelers' preseason home-opening game against Indianapolis, scheduled for kickoff at 8 p.m. ET on NBC.