The fact that merda fans are pissed off to no end should tell you that Guarin is, if not world class, at least a good player, and from what I've seen of Inter he and Alvarez were what kept them going. They suck otherwise.
If he's better than Nainggolan, then that's something, even if he's no Hernanes. If we are getting Berardi/Gabbiadini or someone else from our youngsters next year we are one wingback/winger away from being a CL contender with that kind of depth.
All that being said, I'm sad as hell that Mirko is leaving. I loved that man.