Odorizzi is a serviceable improvement on paper, but I also won't be surprised if they internally think a combination of Pearson, Kay, Merryweather, Zeuch, Thornton, Hatch can either replicate or exceed his production. So maybe they just don't think it's worth it to add anyone who's left?
We're in a great spot with our optionable pitching depth, it's just that a lot of them are unproven. Although most of them are also getting to the age now where they should be producing and aren't really all that 'young' anymore. Unless they make another move, they're probably banking on:
1. a couple bounce backs from the group of Ray, Stripling, Matz, Roark (very possible)
2. at least one breakout from their younger pitchers (also possible)
3. a combination of the over the top offense, sufficient starting pitching, and good bullpen keeping them afloat until the trade deadline where they'll look to add a true top of the rotation starter
So a lot of ifs there, but I could see it happening.