If Semien was totally open to anything, we would have seen him at third base in some capacity. He's a rental (possibly) but he's a vet and is destroying opposing pitching at the top of the line up. Bo is still very young and is an adjustment or two away from being a sustained force in the two spot. If you want to maximize the offence for this year, you have to let Semien bat second with Springer leading off. Vladdy needs to be assured a first inning plate appearance and Teo is entrenched as one of the best clean up hitters in baseball.