Hopkins-Shumenov began extremely slowly with neither fighter doing much in the first two rounds, although Shumenov appeared to have a slight edge. But Hopkins, a notoriously slow starter, began to pick things up and had a strong third round, landing a hard overhand right that got the crowd to begin chanting "BHop! BHop!"
Hopkins continued to find a home for his right hand in the fourth round and although fighting at a measured pace, landed some hard jabs and also cracked Shumenov with a clean right hand to the jaw in the fifth round.
Shumenov, often a volume puncher, was nothing like that, giving Hopkins too much respect. He was throwing one punch at a time and was wide open for Hopkins' left-right combination. In the seventh round, Hopkins stepped hard into a series of punishing jabs that rocked Shumenov.
Hopkins continued to pound Shumenov with counter right hands and then hurt him badly in the 11th round.
Hopkins, who hasn't had a knockout since stopping Oscar De La Hoya with a body shot in the ninth round of a middleweight unification fight in 2004 and hadn't had a knockdown since dropping Joe Calzaghe in the first round of a light heavyweight title fight in 2008, feinted with a jab and followed with a powerful overhand right that nailed Shumenov on the side of the head and dropped him with less than two minutes left in the round.
"I wanted to be patient and not overshoot the runway and get overexcited but I knew he was hurt," Hopkins said. "He went down to one knee and bought some time. Then he started grabbing me and the bell rang.
"But [trainer] Naazim [Richardson] was begging me to throw that six-inch right hand over the jab. I didn't get it off earlier. It was there the whole fight. But he has an awkward style. I've been around 26 years, seen everything and I made the adjustments.
"I was having fun. I wanted to show that I can stand in the pocket. I got hit with some good shots but I never wavered. I tried to stop him. He's tough but I was going for it."
After the knockdown, the crowd erupted into chants of "BHop! BHop!" again and he continued go after Shumenov. Although clearly ahead in the 12th round, Hopkins was still on the attack in the last round and the crowd cheered his every move.
Padilla's scorecard could not be overlooked despite Hopkins' victory.
"Listen, when you get into all that about the judges and all that stuff, they go to school. They have commissions to regulate all that," Hopkins said. "I don't like to get into all of that. It's not my job to deal with that. It's my job to get ready to unify the championship before 50."
Said Schaefer, "That was complete bulls---. I'm speechless. That's another judge who should retire."
The 30-year-old Shumenov (14-2, 9 KOs), a 2004 Olympian from Kazakhstan who lives in Las Vegas, was making his sixth defense and didn't think he won the fight, either.
"To be honest, I wasn't thinking about the scorecards," Shumenov said when asked about the split decision. "Obviously, I chose the wrong strategy. I'm kind of angry I lost the fight. I am a true warrior. I couldn't get the victory. I wanted to fight the best and tonight it was not my best."
Hopkins, however, was at his best, at least as best as a 49-year-old could be.
"I trained so hard. One thing I want people to know before I leave this game is I gave it my all," Hopkins said. "I set out to be the best in the light heavyweight division. I'm thirsty for it like I was at the middleweight division.
"I describe my legacy like a Joe Frazier. We get knocked down but we get back up. I'll let the historians analyze and debate over the years as I grow a deeper gray beard watching soap operas. I'll let them break down my legacy and how it compares to someone else."
And like that, Hopkins left with yet another belt wrapped around his waist, on his way to have a celebratory slice of chocolate cheesecake.