The FC Dallas duo suffered injuries, while Manneh returns to his club side for a preseason tour of Wales.
The reigning Supporters' Shield winners beat out a collection of top Latin American clubs for the services of the highly rated Paraguayan striker.
Benefiting from a pair of top prospects who suffered draft day slides, D.C. United came away the big winners on Friday.
Dan Hunt expects his FC Dallas side to win more trophies after spending money on several additions during the MLS offseason.
The FC Dallas defender has been released from the hospital after a scary incident.