*** SPOILER ***
Well, here's the thing. JDS is just (by far) not a smart fighter. He's a very good boxer, and that's it. I had hopes and thought he could figure out what to do against Cain, but there was nothing new to be seen here.
Here's why JDS is in my ranks as a dumb fighter: he knows Cain will try and close the distance for 5 rounds, and that he WON'T box at a distance. BUT, if you look at the replays of almost all JDS' exchanges, he starts either with a jab or hook, and then throws a LONG punch, either a cross or an overhand, while Cain is (AS ALWAYS) stepping in. Obviously, he NEVER connected a second punch, for five rounds, and HE NEVER ADAPTED.
Lastly, after getting pummeled for three rounds he figured out that elbows are perfectly in range to be used against a guy scraping his chin against your chest. WHERE IS ALL OF HIS MUAY-THAI TRAINING (that everyone mentioned as a hole in his game)? Nowhere, he couldn't figure out how to fit close range muay-thai strikes into his combinations (which might very well be the one answer to a strict dirty boxer like Cain).
JDS is so one dimensional, so much of a strict boxer (and not the smartest at that), that he's either boxing or doing something else (like throwing an elbow here and there), he has no "in-between", and he hasn't figured out a way to put his boxing to use as a tool for fighting an MMA fight (which is all that Cain does), JDS fights to box, and not the other way around.
Just to put clearly how dumb and limited I see this fighter right now, if he knew his opponent would close the distance for the duration of the fight, then everyone and their mothers knew he'd have to work on combinations starting long and shortening progressively. If he had thrown 5 rounds of jab (straight) - hook - elbow, I can bet we'd have seen a different fight. But JDS isn't smart, and his head coach is a boxer who never threw an elbow in his life (which is another sign of how smart JDS is, for sticking with him as a head coach).
As for Cain, he did what he had to, again, and nothing else. There's the difference between the two, Cain clearly has worse boxing and throws mostly awkward unclean punches, but he uses it all way more effectively than JDS, because contrary to the latter one, Cain is a smart fighter, and his boxing is interspersed in a complete MMA game. Either JDS leaves Brazil and joins a big team in the US to learn how to be an MMA fighter (and not just a boxer who can defend TD attempts), or he can hang his gloves up, he'll never be the champion again.