The player to be named later with the Nats-Indians trade has been identified as Andruw Monasterio, a.k.a. the player the Nats got when they traded
raging homophobe infielder Daniel Murphy to the Cubs this past August.
As noted in the comments, this may render the latter trade as essentially giving away Murphy. It’s not clear if/when Chicago and Washington completed their trade, which at the time (Aug. 21), was reported to be Monasterio and a player to be named later or cash considerations.
Occam’s Razor suggests it was indeed cash, which is far less satisfying, but par for the course with Rizzo’s July-August trades of late, where the Nats GM has been more Napoleon than Jefferson.