Take : Unless something crazy happens this is an outfield that could carry the team offensively if Bryce takes off. It is suspect defensively, but I'm not worried about that. Souza and McLouth should make an ok 4 & 5 while Taylor gets ready, though I'd bail on McLouth and try to sign someone like DeJesus.
2015 Reality :Something kind of crazy did happen and Werth and Span both missed big chunks of the year. Werth missed half the year and Span over 100 games. In the mean time the Nats traded away Souza (he'd have the pop & patience combo we all saw, but he'd have the low average we all saw as well) and McLouth didn't play the whole year thanks to his own injury. So instead of Bryce - Werth - Span backed up by Souza, the Nats spent part of the year with Bryce - Taylor - Robinson backed up by Moore. Ugh.
It could have been awful and parts of it were. Taylor couldn't hit. Robinson was not good in the field. Werth had some injury related troubles at the plate when he did play and very few balls were hit into the glove of what I assume was the Madame Tussaud's wax figure of him the Nats installed in left field. Tyler Moore was the same big ol' nothing he's been for 3 years now.
However, Bryce nearly single-handedly saved the offense by becoming BRYCE. He put up one of the best offensive seasons of the past generation and his defense was ok to boot. That alone makes the outfield not a loser. Other high points were MAT's stellar defense and Clint Robinson's effective bat.
Basically it was the best of times, it was the worst of times so on average it was the ok of times.
As for my DeJesus idea. Not a great year (slightly below ave in TB before dying in LA)but at least he played.
Out of the box :Trading Giolito to the Brewers for Carlos Gomez would have not been enough to make the Nats a playoff team. He himself wasn't healthy either and when he did play he put up meh numbers. He was still good in the field and having him instead of Span/Taylor would have made the Nats better but not to any degree that they would have at some point run away with the East which was the goal.
That being said, if you like him he'd still be here in 2016 with a cheap contract, solving the whole "Span is hurt all the time, but Taylor can't hit" conundrum. However, all in all without that playoff in 2015 he'd have to spark a deep playoff run in 2016 not to rue that trade.