Froch rounds 5-8 IMO. Mack typically gets broken down around that point by the better names and I wouldn't think it'd be any different with Froch. He's not well-versed enough or physically strong enough to keep Froch off him so I think he'll get broken down as soon as Froch's heavy-hands start to take their toll, though I don't think he has the true power to take Mack out that early.