If you watched yesterday's game, especially Joba's domination of Willy Aybar, you should understand why Joba is a starter in the long-term.
Gameday uses its cameras to keep track of each pitches break in two different ways. The first, which they call "break," is a simple measure of the distance between the farthest extremes of the balls movement. The second is called Pf/x, and I'm not going to worry about it in this post.
Joba started Aybar out with a curveball that broke more than a foot; that's Joba's third best pitch (he's also got a changeup that is above average).
Joba came back with a fastball clocked at 101 in the stadium (the gun is juiced, Gameday clocked it at 96), but a fastball down in the zone with some wicked sink on it. Again according to Gameday, that fastball broke 4 inches. As a point of comparison, Wang's sinker breaks 6"-8", while Mo's cutter breaks around 5".
Joba then finished Aybar off with an 85MPH slider with an 8 inch break.
This is a pitcher built to go through a lineup multiple times- he won't always be this successful, but he's going to rank among the best pitchers in the league once he's built up the endurance to log 180-200 innings. One of the other prospects can scrap his third pitch and serve as the bridge to Mo- by midseason, a couple of them will be ready (Chris Britton and Jonathan Albaladejo are ready now). Joba needs to start as soon as possible.
I hope Moose pitches well tonight.