Rios has became a bit underrated as of late (mainly by people trying to say Pacquiao only beat a complete bum) but Brook will win a wide UD here.
If people are picking him over the likes of Mayweather, Pacquiao, Alvarez...etc then sure, he's overrated. But Rios?, come on now. Rios is a walking sandbag. Brook will have a field day outboxing him and landing at will.
What since he lost to Pacquiao? And what happens when Rios lands on him or gets on his chest? Rios would do a lot better than Porter and hit Brook harder than Porter did. And probably wouldn't tire as quick. Rios was a punching bag for Pacquiao... Brook is no Pacquiao.
Brook UD If he can handle the strength of Porter on the inside he can handle Rios. Not to mention Alvarado outboxed Rios on the outside Brook can to.