There are literally hundreds of mock drafts around the Internet put together by all different kinds of people in completely different walks of life. When almost every single one of them thinks that the Steelers need an offensive lineman, it should say something about the state of that unit. Dane Brugler at CBS just came out with his latest mock, and he has the Steelers taking Keleche Osemele, a guard out of Iowa.
It doesn't matter how tough Ben Roethlisberger is, the human body can only take so much and the Steelers need to address the offensive line in a big way this offseason. Osemele has the skill-set to play both tackle and guard at the next level and has the strength and natural ability to start early in his career. He's a similar prospect to Ravens RT Michael Oher when he came into the league.
The Steelers' entire offensive line was a problem last year, and they probably need to address the guard position in the draft, whether that's in the first round or elsewhere. They chose tackle Marcus Gilbert in the second round last year.