Well, apparently Evoaldi isn't going to be the answer because he's going to the pen, and unless his name is Wright I don't see anyone on our current roster with a good chance of filling that spot.
Were I sitting in DD's or JH's chairs and trying to assess the future impassionately I'd be asking how much money I'd be willing to pour into a team that's 11 games back of a very good Yankees team.
Here's what I wouldn't do: I wouldn't go out and sign anyone for big money in the hope of overtaking the Y's. It could happen but the odds are significantly against it. I also wouldn't be looking for a position player. IMO our position players are good enough to get the job done as they're doing, and when JDM and Mookie start hitting better the team will once again be an offensive juggernaut.
That said, here's what I would do: I'd be beating the bushes for a decent #5 guy who could be had 'on the cheap' much like he picked up Brazier last year. I'm not sure what the definition of a #5 guy is but to me he's got an ERA of between 4 & 5 and a WHIP of ~1.20 - 1.30. That's not great but one doesn't get "great" on the cheap. If you can get six innings out of a guy with an ERA of 4.5 he's only giving up three runs and that's not an insurmountable amount for this team. (See: Ryan Dempster)
As far as the top 4 in the rotation goes, we're pretty much stuck with what we've got if we intend to make a run at the WC spot. Giving up one or more of Price, Sale, Porcillo, & Erod would be paramount to waving a white flag. We've got to hope that these guys (plus Wright) can come around and give this team what it needs.
A WC spot not only could happen it probably would, but the team still needs the tweak to make it a bit better.