One of the writers from Baseball Prospectus was asked the following:
From the fall/winter leagues, it would seem that Amador is playing his way into the conversation for the opening day lineup while Singleton is not. Come April, which one makes the opening day roster, if any?
And if you click the link, you'll find the answer. Basically, Amador is going to get every chance to stick in Houston before Singleton, because:
a) Amador is 27. Singleton is 22.
b) Amador is who he is, might as well see what he's got at the Major-League level
c) Singleton struggled in 2013 after that 50-game suspension, so he could use the time Amador is given in Houston to refine his skillset.
Of course, the response is far more eloquent than that, but good points all around.
Update: OKC's radio man Alex Freeman has a post up on his blog regarding many things, but for our purposes here, let's look at his remarks on Singleton:
Everyone in the know is certain 2013 was an aberration for Singleton, and he’ll bounce back next year.