Given Bragg's options to attack from Kentucky (or lack there of) and the rail network, it's almost a nonfactor really. I have no idea why Lincoln wanted it so badly when manpower, tactical deposition, railroad network, and supply capability don't justify it being hugely important. His options of supply are looting or never advancing past Lexington. The South's manpower situation isn't improved even if we assume many eager recruits (unlikely given the state voted in people who were unionists). So if Kentucky has no effect on Nashville, I'm not seeing this really significant.