They just don't have that many that fit that category....those might be the only 3 and, to be truthful, not sure what their market value would be. This, to me, was a year where it was "win or bust"....a bridge year where if everything went right they could repeat the last two years' successes while, essentially, giving the farm 1 more year to build up some prospects after it was totally depeleted by AA's roll of the dice in 2015.
Obviously, in the early days, they are far from "everything" going right....and it is looking more like it going bust than being a "win"....but, it is still only April and lots of baseball left to play.