Justin Bieber -- 'Crazy Athletic, Real Potential' ... Says Ex-Boxing Champ

Justin Bieber's no bitch in the ring -- the guy's got REAL BOXING POTENTIAL ... so says former champ Andre Berto who says Bieb could be a real contender if he takes the sport seriously. We spoke to the former welterweight champ -- who trains at…

Mýa Nadine Velazquez Naomi Watts Natalie Imbruglia