The Nats head into the last 70 or so games looking like they'll stick to the same plan in which they started the season. Keep everything the same and hope it all goes according to plan. It doesn't sound like a good idea but the Nats don't really have a ton of better options.
It's the offense that has failed the team but now that everyone is finally healthy and playing together I don't see anywhere they could make a deal and substantially improve the team. Really, who do you trade over? Span is the only real option and the possibilities here don't excite anyone. Trade for De Aza and have a terrible fielding OF? Take a chance on Denorfia? Move Bryce over, trade for Alex Rios and hope he hits better? The only move worth making is for Stanton and the Marlins wouldn't trade him for anything less than the entire Nats farm system (if they'd even trade him in division... if they'd even trade him).
No, the Nats made their OF move and that was trading for Hairston. He should play vs tough lefties while Span sits. Not really anything more you can do.
In the infield everyone is entrenched so unless you want to do something radical like trade for Morse and platoon him and LaRoche (not a terrible idea if Morse is being given away), again we turn to the bench. Given that the starters are all good with the bat, really the bench has to be glove-focused. There are plenty of back-up glove men available for a song out there, but why deal when you have one in the minors right now in Espinosa? Bring him back up, say bye bye to Lombo and there you go. Easy fix.
I suppose Tracy could also be replaced but there aren't many decent lefty bats out there. Ibanez? He would cost too much to park on the bench for 90% of the time. I'd say if anything bring up Steven Souza and see if he can pull a Tyler Moore 2012.
So that leaves pitching. A month ago a LH relief pitcher would have been paramount but both Abad and Krol have been good enough to no longer feel that's necessary. One of those guys, Soriano, Clippard, Stammen and/or Mattheus, Ohlendorf in long relief. That's really enough. When you are bringing in the talented but flailing Storen as the 5th choice out of the pen, you have a good enough pen.
We're down to starting pitching. Assuming you like Detwiler enough (or want to give Haren another try given his decent last start) the Nats would only be aiming for one pitcher and it would have to be a good one to make an impact given that they are going to start probably 13 times. Garza is likely gone elsewhere so what's left for the Nats?
Phil Hughes is on the market as the Yankees have finally accepted that his homer issues make him a bad fit for that park. Love AL to NL moves but not really the difference maker. John Danks has pitched better than his ERA would indicate (1.133 WHIP), has been very good in the not distant past, and isn't old. But he's owed 14 million a year for the next 3. You'd be choosing him over ZNN or vastly upping your payroll. Kyle Lohse is more intriguing as he's pitched very well for 3 years now. Unfortunately he's 34 and under contract for two more years after this. James Shields / Ervin Santana - the Royals may listen to offers for either one and both would be worth offering. Ervin is a FA next year though and Shields has only one year left. While that may appeal to other teams, the Nats tend to want to deal for cheap control. Jake Peavy also offers an interesting possibility if healthy.
After all that though, I don't think the Nats deal for any one of these guys. A Santana-type move would be a classic contender move (its what I would suggest. Well actually I'd suggest going after Shields first) but the Nats have shown no inclination to make that sort of deal. Is there anything out there that they might pull off? If they had a better farm system I'd say they may try to throw it all at the White Sox for Sale, but I don't think the Nats have the chips to pull something that crazy off, not unless they want to include Rendon. So what do I think they do? Maybe surprise (disappoint) everyone and toss a few of their decent but not exciting prospects at the Padres for Andrew Cashner. Young, in team control for a while, groundball pitcher. Yes, he has a bad home/away split but the fancy stats suggest it's a little fluky and he actually pitched better away from Petco last year.
That might be the extent of it, if the Nats even go that far. I could see them easily doing nothing. That's the problem with putting a team together on paper that should dominate. If they don't get injured it's hard to find guys out there you like better than the guys you already have. You either have to break the bank on one of the best players in the game, or you gotta make a bunch of minor improvements, each one at a pretty hefty cost themselves.