Which of these do you consider a can?
John Duddy? 29-1 (9 wins over top 50s, several over former titlists)
Troy Rowland? 25-2 (3 solid wins)
J LeHoulliere 21-1 (2 draws in high level regional title fights)
Lucian Cuello 31-1 (won both regional titles he fought for, lost only to JR and Alvarez)
Matta Vanda 39-7 (solid top 20 his entire career)
Tobi Loriga 24-0 (5 minor titles)
Jose Celaya 31-3 (3 minor title)
And I could name several others such as Carlos Molina who is a TOP 10 for the last 4 yrs, Ray Sanchez who was once a very promising prospect. You can't say any of these guys are/were cans when they chose to fight JR.
You can't even make a comparison here.
Maybe, just maybe you could compare Potvetkin to Chavez. Being that he fought dozens of solid contenders before finally fighting the man in his division, but a better comparison would be Vaugn Bean. A Chicago banger who never met a can he couldnt crush.
Another HW, active, would be David Rodriguez. 36-0 34KO, who shares a common oppnent with Wilder. ie Beck. However, Rodriguez was slated to fight Boystov, and has been calling out Arreola, Fury, the K2, Mitchell, and a host of other top 50 HWs.
Wilder has trash talked ok, and he had a decent excuse earlier in his career, about his wife being sick, but if he started calling out names, you can best believe he'd get a fight.
It's looking more and more as if he's being protected.