Broner's defense needs some work. But, it's not that bad. Against a guy like Mathysse, it's a bit more of a liabilty. His heart makes up for it. I'm not sure how much smarter a puncher Mathysse is than Maidana. Maidana keeps his chin tucked when he punches. And that awkward chopping overhand right was made to penetrate a defense like Broner's. Matthysse is a very good puncher, but, if you punch WITH him you can put him down. We've seen that already. Broner has the speed and enough pop to do that.
I'm not sure Carlos Molina has been down in his pro career. Correct me, if I'm wrong. He's a sturdy guy. He took losses to more skilled fighters like Khan and Broner. But, that's about it. Mathysse is better than Carlos Molina. But, he has been on the canvas, in 2 fights (2x against John Molina), back to back. So, it was not a fluke. When he is punching is when he can be caught. I don't know if Broner can beat him. But, he has what it takes to check Lucas's chin.