Starks, who has started every game for Pittsburgh on the right side since the beginning of the 2005 season, injured the knee last Sunday, although Steelers officials haven't determined exactly when. It is believed Starks may have suffered the injury in pre-game warmups, and then played the entire way in a 37-3 victory over the Carolina Panthers.
The loss of Starks, 24, means that either second-year veteran Trai Essex or rookie Willie Colon will start when the Steelers host the Baltimore Ravens on Sunday. A fourth-round pick, Colon has not dressed for a single game this season. Essex started four games at left tackle in 2005, when starter Marvel Smith was injured, but has never played on the right side.
Baltimore's 52 sacks are second in the league to San Diego's 54. The Ravens sacked Ben Roethlisberger nine times in a 27-0 victory over the Steelers on Nov. 26; this would present a problem for Pittsburgh's offensive line even if Starks was healthy.
A third-round choice in the 2004 draft, Starks appeared in nine games as a rookie, with no starts. Some in the organization questioned how good a player he would become, but when veteran Oliver Ross departed as a free agent in the spring of 2005, Starks moved into the starting role and has been a fixture there since.
The former University of Florida lineman started every game in the Steelers' run to the Super Bowl XL title in 2005. He's started all 14 games this season and has become one of the best young right tackles in the league.
Brown sprained the medial collateral ligament in his left knee, an injury that might end the 14-year veteran's career; he was signed at midseason to help compensate for injuries at the position. Iwuoma, released in camp and then re-signed early this month, suffered a dislocated wrist last week.
Senior writer Len Pasquarelli covers the NFL for ESPN.com.