Barker and Macklin both took several rounds off Martinez, Froch is probably 2 levels above either of those guys and much bigger than either of them, Froch by ko/tko in about 5 or 6 rounds imo.
Some that are suggesting that Froch would easily walk through Martinez are foolish as are the others who are picking Sergio to win comfortably or stop froch are the exact same. Sergio can step into top gear whenever he wants (late on against Macklin and Barker) and this version is much better than the one that baits his opponents to wear them down (early against Macklin and Barker) he would have to start of quick against Froch otherwise he's in danger of being stopped early (like Bute) or losing to many early rounds. Sergio also poses a tough style for Froch as well as vice versa. Sergio is used to people coming out quick against him, however Froch's stamina is second to none and wouldn't gas from the mid to late rounds. On the other hand Sergio is a southpaw and has good head movement. We saw Dirrell have success pot shooting against Froch and arguably won the fight and maybe this could be the best way for Sergio to approach the earlier rounds and try to come on strong late. That being said his head movement and speed are not up to the standards of Dirrell so it's questionable whether this tactic would be that effective if at all I personally feel the main factor will be the size. Froch is naturally heavy handed, much like Sergio however, I don't think Martinez gains much power in his punches from moving up just the 8 pounds. Froch won't be able to just walk through Martinez, but I can't see it bothering him that much, whereas I could see Froch's power in accumulation of punches being enough to stop Sergio or at the very least wobble him a few times In all i think it would be a fairly even fight throughout, but being more established at the weight, Froch would get the better of the action early, maybe even dropping Sergio, whilst they go fairly even through the second half of the fight. 115-112/116-112 style UD for Froch
Froch is too big for Maravilla. Maravilla should not fight above 160, and may be even better at 154. Froch must look up instead of down. 175 would be a nice division for him.