The Steelers have to address their offensive line or their franchise quarterback is going to continue to get hurt. Big Ben has been fantastic for the Steelers in being able to extend the play and take some hits, but they can't keep letting him take those hits. Osemele offers the versatility to play tackle or guard, which helps justify the slight reach for him. The Steelers have suffered lots of offensive line injuries so Osemele's versatility provides much needed depth as well.
Osemele certainly makes sense from a positional standpoint, although the Steelers aren't generally too keen on reaching for players in the first round unless their evaluations of the players involved are very different from those of other teams. They certainly won't do so purely out of need. Osemele will certainly be on the Steelers' radar, but if he's the best guard on the board when they pick, they could easily take someone else and hope he falls to them in the second round.
Penn State's Devon Still falls to the Tennessee Titans at No. 20.