I know this is going to stir up a Hornets Nest, but Burton has not been the best reliever in spring training so far. 4 games, a 9.00 ERA, 8 hits, 4 runs, 4 earned, 2 HR, 0 walks, and 3 strikeouts. I know everyone has considered him a lock, but he really has not been overpowering in spring training.
I am not aware of whatever options he may have, but I think you might consider sending him to AAA. Bullpen spots are at a premium, and you don't let him go north if he will not be ready. He has spent his year on the roster, so I believe he can be sent to AAA now if we need to.
I do hope he does better and is one of the players to start Opening Day in Cincinnati, but I think you have to consider starting him in Louisville as well.