The move was made before Sunday's game against the Mets.
Maya was with the Nationals for less than 24 hours. He was recalled on Saturday as a fill-in starter after Jason Marquis was traded and pitched 5 1/3 innings in a 3-0 victory.
The 26-year-old Severino went 1-0 with a 3.00 ERA in 23 relief appearances with Syracuse this year. His first appearance with the Nationals would mark his major league debut.