I use Peyton Manning as I usually only play with the Colts. He doesn't have the speed to get away from pressure but he can step up and use blockers to take away the pursuit angles of blitzers. Addai is a great pass blocker so what I do is use him as my guy to adjust around. Sometimes the hot read is covered and you need more time. Basically, If I see pressure coming from one side, I sidestep,step up, or a combination of both so the HB takes away the blitzers pursuit angle.
Having an extra blocker in the backfield instead of an extra blocker on the line gives you someone to sidestep around. This can help improve your pocket presence and allow for longer developing passes.