NASHVILLE—As if he wasn’t expecting it, Rustan Rigdon fell back a step in the moments after bumping chests with Mike Mancini. You’d think by this point Rigdon would’ve expected something like this to happen, but he went against the odds and fell backwards.  Mancini and Rigdon’s chest bump had just came after Mancini’s second homer of the night and Vanderbilt’s 100th of the season. Perhaps this hasn’t all gone to plan, but the moment was symbolic of everything that’s gone right for this program this season and everything that went right for it on Tuesday night.  “That looked like I can dunk,” Mancini joked in regard to his jumping chest bump with Rigdon. “I hit him hard. I think I got up to like 10 feet.…