From looking at his body, he's definitely old. I'm thinking he may have got his rack caught in a fence or something. I saw pics of a similar buck my nephew had in North Dakota that got caught in a fence while in velvet. Either way.....he's old!
More than likely an injury to opposite side. Doesnt look broken off so from earlier and usually a velvet infection makes some crazy stuff happen. I would say this old warrior got hurt on his left side well before antler growth and it took its toll this year.