Good article by J.J. Cooper at Fanhouse, who counted the snaps from the NFC Championship game. In that game, the Green Bay Packers NT B.J. Raji was only blocked by the center on seven plays out of sixty-one snaps on which Raji played. That's largely because the Packers often played with only two defensive lineman on many plays.
I think that's an extreme example. Though I haven't counted the snaps from every game this season. Instead, I expect the Packers will play with three down lineman on more plays against the Steelers running game. In that situation, I'd expect C Doug Legursky to double-team on Raji with one of the guards. Also, I don't expect Legursky to pull as much as someone like C Olin Kreutz.
While Raji will take on Legursky in some passing situations, I'm looking forward to watching how Legursky matches up against the blitzing linebacker up the middle.