Danno

I wonder if the real reason Haz is playing Grant and Watson at MLB instead of one at MLB and the other at WLB is that he knows neither may stay healthy the whole season.
Like WhoDat said, rookies rarely make it all 16 games. Its too much of a shock and they aren't used to the demands on the body yet.

Grant appears to be a bit injury prone so I imagine Haz is a bit hesitant to depend on him for 16 games.

Playing both gives him some injury insurance/flexibility in case one goes down for a few games.
I wonder how easy it is for an atheletic MLB to shift over to WLB? Maybe their best training method may be to learn the very difficult MLB position first and the rest is a relatively quick adjustment.

Its a win-win. Between the two he has a solid atheletic MLB for the whole season, and the loser plays back-up to both MLB and the WLB.