One of the realities about this sport is that most often, fighters go out on bad losses. Boxers don't usually leave the game on the top or off of a win. Generally, boxers leave the sport on a bad note and thats the nature of the game, for all races of boxers.
Fighters like Joe Calzaghe and Rocky Marciano are extremely rare in that respect, in that, that never happened to them (which truly shows how great and underappreciated they are).
Dzinziruk's best period was probably from 2004-2008. I remember watching Dzinziruk fight Daniel Dawson in 2010, and I thought Dzinziruk looked a bit "flat" if that makes any sense. Not a lot of strength, not a lot of power in his shots, lacking an overall sharpness. I also saw his TKO loss to Martinez, and his draw to Gonzalez (where I thought Dzinziruk showed a lot of heart).
Dzinziruk is a warrior who always gives it his all and he deserves a lot of credit for that. Truthfully though, I think he's been in decline for several years now. 2004-2008 was his prime and since then he's been going downhill. As I recall, he had some promoter issues with Universum at the time which resulted in him being extremely inactive.
He really should have fought more often in that time period (2004-2008), because now, that window of opportunity is gone. He probably could have unified at that time, because he was much sharper then. Dzinziruk probably could have accomplished a lot more in his career if he had been managed effectively, he had too many problems with his manager Universum and that took away too much time from his peak period. Its unfortunate.
Anyways, Brian Vera is a very tough guy and there's no shame in losing to him. Sergey always gives his all in the ring and he's a great fighter to watch! Who knows, maybe he can comeback from this. But another loss and I think its time to reevaluate things!