The 2013-2015 Kov beats Calz IMO. Enough firepower to seriously hurt and deter Joe, and a heavy, consistent jab to keep him off balance.
Calzaghe clearly. Kovalev didn’t have a great engine. Calzaghe isn’t dumb enough to trade shots with him and would do well enough boxing in and out before taking over when Kovalev tired.
Kovalev would fold under the pressure Calz puts on him. Joe by dominant UD, maybe even tko of Kov quits.
Tricky to rate Calzaghe against genuine, career 175 pounders because he only had two fights at the weight, neither of which really told us anything about him. But he was a big Super-Middleweight who complained for years that making 168 wasn't easy (one of my pet peeves regarding his excuses for the bigger fights not materialising until later in his career), so while he'd be the smaller man against Kovalev I don't think it would be by a great deal. Ward was another relatively big, strong and fast Super-Middle who was able to move up and beat Kovalev (though not without controversy, admittedly), but he had a very different style to Calzaghe and one which was better-suited to taking advantage of Kovalev's flaws. A lot of Ward's success was built on being busier and outmuscling / smothering Kovalev on the inside, as well as using body shots. But Calzaghe was no inside fighter at all, and while he could mix combinations between high and low I felt he underused body shots, and was more of a serviceable puncher downstairs than a particularly damaging one. He was also very hittable and prone to the occasional early knockdown, so he's going to have to be very careful, particularly in the first few rounds. Calzaghe had a good chin, but Kovalev would be the biggest puncher he's faced by some distance and that move up in weight will likely further underline that. That said, Kovalev enjoyed staying in the pocket and exchanging shots when the other guy was throwing, too, and if he fades late on as he occasionally has then he's going to have some problems of his own. I guess a lot depends firstly on whether or not Kovalev's power is too much for Calzaghe - and if it's not, then how Kovalev goes about shutting down or negating Calzaghe's speed and work rate. People assume Calzaghe threw around 1,000 punches in every twelve round fight, which isn't the case. If you could smother him inside (I'll say again - Calzaghe really couldn't fight very well there) and make it scrappy by staying right on top of him, his output dropped a lot. Starie, Bika and Hopkins all did this and made him look ordinary, albeit the first two didn't have the additional required class to make the fights particularly close. The other way of offsetting his work rate is by keeping it long and preventing him from getting into the scoring range, but although Kovalev had (or has, depending on what you think he has left) a very good and heavy jab, that wasn't really his game and he always gave you opportunities to land. If Calzaghe can stand up to Kovalev's power, then I think Kovalev might have serious problems as while he's better and probably stronger on the inside than Calzaghe, I'm not totally sure he's comfortable enough there to shut down his hand speed and engine. Gun to my head, I'll say that Calzaghe is a shade too hittable and starts to feel the difference between good punchers at 168 and very good punchers at 175, getting slowed a little by Sergey's power, especially if Sergey has success to the body. I think Calzaghe makes it the full twelve, but loses a very narrow decision, possibly in part due to an early knockdown which I could envisage. Kovalev's more proven class at the higher weight make me lean towards him. But again I'll stress, a lot depends on how Calzaghe stands up to the punching power, which is a clear step up from anything else he'd have experienced.
Kovalev beat Ward in the first Kovalev-Ward bout imo. He wasn't the same after getting shafted in that. Kova at his 175 best was a big puncher and an underrated boxer. I rate Joe very highly, great fighter, but if Calzaghe can be put down by Hopkins and post prime Jones at 175, Sergey might keep him down. If Joe gets through the early rounds and can unsettle Kov, he can make this very close down the stretch with his flair, heart and workrate. He will be winning rounds and has a real chance if he can negate much of Sergey's work. I wouldn't write him off in this. At LHW, I would favor the power of Kovalev to prevail, but on points in a fairly tight UD, as I feel although it might be close in rounds won, he might have scored a couple of knockdowns.
