Why is beating Arreola seen as a big deal?

Arreola has no big win as such but he has a few decent wins.
McCline(albeit past it) and Minto are probably his two biggest ones, he's also got the wins of Chazz Witherspoon, Travis Walker and Israel Garcia, aswell as a good few other Americans with good looking(but very padded) records.

He's legitimately a top 10 Heavyweight, and I suppose beating a top 10 Heavyweight is always going to be a big deal to some degree(even when it's the Klitschko's doing in against someone lower down the list).

It's the fight which will now see Adamek himself recognised as a top 10 Heavyweight, considering it's not long ago he was a Light-heavyweight you could see how that's a big deal.