SBW is the worst "in" fighter I have ever seen. That's because he has never fought anyone of any real ability, therefore he has never really had to truly box to win his fights. He stands back and tries to land big shots, just like he would train on the heavy bag at the end of a training session.
A bloke like Paul Gallen might worry Sonny more. Someone that can keep moving forward, take a bit of punishment, get in close, work his ribcage and he drops his hands every time to protect his mid section. A quality boxer would have little trouble landing an upper cut and left hook on Sonny's chin and jaw.
Then it would be goodnight Irene!