1
Supposing that the rookie Kelley threw (1) a great fastball, (2) a quality slider and (3) a show-me changeup, then... he's not going to throw any changeups at all in short relief.
So, no telling how good his change is or isn't.
...................
Definitely easier to make the majors in the bullpen, no surprise there.
As to whether the M's view Kelley as a Mark Lowe type, just no way his arm holds up to starting, that's a good question.