He doesn't, if he's injured (it would just carry over to next year). But he's not that injured. I doubt he's the next guy up though.
I don't think it's hugely mysterious why the team is struggling! They are missing 2 of their best hitters and one of their three best starters and the other two may or may not be worn out a little from last year still. Ditto the top relievers, while the two new ones they got are both disappointing. And neither Walker nor Falter could be expected to give you long starts. But I was hoping we'd see a .450-.475 team not a .333 team while they ride some of this out.