I ran across this article on a breakdown of Steeler blocking responsibilities on some running plays in the Bear's game. They specifically talk about how well DeCastro pulls. A couple of interesting items in the article. One is that when Foster pulls he keeps his head down which causes him to miss blocks. The other is how often Sanders is mentioned on how well he blocks.
[URL="http://www.behindthesteelcurtain.com/steelers-film-room/2013/9/27/4768578/steelers-GIF-offensive-line-analysis-breakdown-film"]Steelers Film Room[/URL]