Kovalev wins it by KO. Cleverly would box circles around Shumenov. Clev/Kovalev is a 50/50 fight IMO.
What evidence past or present indicates that Shumenov would get blown out? Probably wind up being far more competitve than most would have ever imagined.
It'd be a crazy war. Kovalev's precision and power meeting Shumenov's volume output. Shumenov has shown to have one helluva chin (dropped by Uzelkov once). I'd pick Kovalev by a KO somewhere around 8 after Shumenov gasses ala vs. Campillo. --- As for Cleverly, I'd pick both Kovalev and Shumenov over him. I think he's highly overrated.
I don't think Kovalev would stop Shumenov, but would win a decision. He could possibly stop Cleverly though. Then Cleverly probably outboxes Shumenov.