Dylan Carlson
When I was first starting this list, I was going to argue for optioning Dylan Carlson at this moment. Then I switched to Burleson, and then I switched back to Carlson, and here is why.
Carlson still has a ton of talent and is not a bad player, but his ability to hit right-handed pitching is just non-existent right now. He needs to figure that out, especially if the club is going to move on from a Tyler O'Neill in the near future.
Burleson, unless he just doesn't come out of his slump, represents a weapon off the bench for the Cardinals, and then can operate as the fourth outfielder when rest days are needed. Carlson can have some time in Memphis to work things out and hopefully return to St. Louis as an everyday player.
I also just believe, like O'Neill, that there is too much talent in Carlson's game to underperform as he has to this point. I think both O'Neill and Carlson would improve a lot if they are playing more often, but there just isn't enough opportunity in St. Louis for Carlson to get those at-bats right now.
Who gets called up in place of Burleson then? Well, the Cardinals still have a 40-man roster spot open with Taylor Motter's DFA, which makes me think they have a corresponding move in mind if they were to option one of the outfielders.
Oscar Mercado has been pretty darn good for Memphis this year and is someone you don't have to worry about playing all that often. He can provide the defense late in games Carlson could provide, but not need to get starts outside of clear rest days for their starters.