Nolan is solid on D. The problem with Brimah against someone like Okafor is that Brimah tries very aggressively to block everything and tends to leave his feet when he doesn't need to. I think what Dom was trying to say is that a player who has all the moves of Okafor could eat Brimah up meaning 3 quick fouls in say 5 minutes. Once that happens, in comes Nolan. Nolan is a guy who plays a more traditional straight up defense and that might be a better recipe against Okafor.
From what I saw against Michigan State the best stretch of defense they played on Okafor was when they put a big, physical, talentless white goon on him who pushed Okafor off his spots. That is how you slow down a guy like that - put a big strong body on him and knock him off of his spots, disrupt him, break his rhythym. Unfortunately neither Brimah nor Nolan have that kind of body. Okafor is probably stronger than both.