Here's something that might surprise you. The Nats offensive starters have this line :
.253 / .311 / .408
That batting average is league average. That OBP is a little below league average. That SLG is a little bit above league average.
But the Nats haven't produced like an average offense. They've been better than that. They've been good. How is that?
It's because, for one reason or another, the Nats hitters are great when they don't start the game.
One thing we can look at is pinch hitting. The Nats have a line of .315 / .409 / .473 when pinch hitting this year. That's good enough to be head and shoulders above the rest of the National League.
But it goes beyond that because being a substitute isn't just being a pinch hitter. All those at bats after that count too. And nearly every National that could come off the bench in this role has hit better as a substitute than when they start.
Starting : .283 / .360 / .388
Subbing : .395 / .490 / .488
Starting : .219 / .265 / .438
Subbing : .323 / .405 / .548
Starting : .274 / .317 / .355
Subbing : .357 / .438 / .429
Starting : .277 / .342 / .505
Subbing : .310 / .375 / .517
Starting : .085 / .214 / .085
Subbing : .316 / .458 / .526
Starting : .226 / .275 / .376
Subbing : .240 / .321 / .600
Starting : .131 / .180 / .190
Subbing : .278 / .350 / .667
Their sub line is .319 /.415 / .486. The next best in the NL is the Mets with a .262 / .344 / .440 line. Is it Davey making the right moves? Is it Rizzo putting together a decent bench? Is it just dumb luck?
I don't want to dismiss the other two but it's a lot of #3. Generally, your at bats as a sub are going to
be limited so you are going to see a lot of variation compared to your stats as a starter (pure pinch hitters like Chad Tracy excluded). Some people should find themselves doing worse, some should find themselves doing better. And it can be radically so, averages closing in on .500 or well below .100. What we see here with the Nats, with everyone improving when they aren't starting, is really very fluky.
As for the first two parts, I'm not sure. The Davey role is something that would need more investigation. He can't place the guys in situations so that they'd perform this well (remember too that this includes post PH at bats that Davey has less control over). However, he could have a history of having most of his guys do slightly better at PH than expected. I'm not going to discount that out of hand. The Rizzo role, well... I have a hard time saying that DeRosa and Nady constituted a good bench. You see what they've done when they've started. Their sub success is the most flukiest. You may not have expected the other guys to do this well but there are decent players among the rest. Bernie can spot start. Lombo can get a single. Moore has legit major league power. You kept Ankiel in part because he might blast one. Tracy was brought in to pinch hit and he has. Maybe Rizzo didn't personally set out to get all these guys on the Nats (Bernie has been the 4th OF for what? 18 years now? Moore forced the issue through his play and injuries forced the move) but in the end he's responsible for who's out there, so he gets the credit if they do well.
Can the Nats keep this up? Sure, why not. It's just a few at bats. A better showing from the guys that start the game would be nice though.