FanHouse Ryan Mundy

The Steelers survived their season-opener after losing Troy Polamalu to injury. They're going to have to figure out how to live without their superstar safety for a bit longer.

Polamalu confirmed reports that he suffered a sprained left MCL in Pittsburgh's Week 1 win over Tennessee last Thursday, and told the Pittsburgh Post-Gazette that he will miss three-to-six weeks.

"Regarding a knee injury, this is the best-case scenario," Polamalu said Monday.

If you're looking for a lesser-known rookie in Steelers camp worth keeping an eye on as training camp begins, the player to watch apparently is Keenan Lewis.

The Steelers' third-round pick out of Oregon State was mentioned as a dark horse for team rookie of the year by Steelers' beat writer Jim Wexell. Now SI.com's John Lopez has also singled him out as a rookie who could make an impact.

The scouting report on Lewis was that he had very good size and good enough speed. Apparently he has pretty decent instincts as well. The good news is that more than almost any other position, cornerback is one where how a player looks in shorts and a helmet isn't that different from how they look in a full-contact practice. Unlike linemen, linebackers, running backs and wide receivers, it's more about how they react to the ball and the receiver then how they react to hitting and being hit.

So which 2008 Steelers draftee do you think the team most needs to step up in 2009?

You could argue Rashard Mendenhall, the team's '08 first-round pick, but then if he falters, Pittsburgh still has Willie Parker and Mewelde Moore (last year's primary backs on a Super Bowl champion) plus Frank Summers.

Or you could say Limas Sweed, the team's second-round pick last year. But if he can't handle the slot receiver role or he keeps dropping passes, Pittsburgh has signed Shaun McDonald as a back-up, while rookie Mike Wallace could be a decent replacement as a deep threat.

If there's one 2008 Steeler draftee who is being counted on more than any other, it's Limas Sweed.

Even a year after he was drafted, first-round pick Rashard Mendenhall will be the No. 2 tailback, but even if he fails at the job, Mewelde Moore and Tank Summers are available to step in. Third-round pick Bruce Davis and fourth-round pick Tony Hills will need extremely impressive training camps just to make the gameday roster, fifth-round pick Dennis Dixon is likely the No. 3 quarterback while sixth-round pick Ryan Mundy is battling for a roster spot.