Performance aside - although obviously this will be a big factor - it's going to depend on the usual evaluation criteria for pitchers. Can he stay healthy, can he go deep into games/maintain his stuff deep into starts, and how does his third pitch develop? Manoah is probably an MLB ready dominant 1-2 inning reliever if he wanted him to be right now, but as far as I'm aware he didn't really show his changeup too much this spring and like every other pitcher his appearances were short so we don't really know if he's capable of going 6+ strong innings while not losing much efficiency of his stuff and going through the lineup multiple times without getting shelled.