Carroll was on the Nationals' opening day roster and appeared in five games before being designated for assignment. The 30-year-old went 0-for-2 with two runs scored with the Nats and batted .250 with 10 home runs and 50 RBIs in 111 games at Syracuse.
The former 10th-round pick of the Marlins in 2004 was signed to a minor league contract by the Nationals last offseason.
Maldonado appeared in four games with the Nats this season during a stretch when it seemed every catcher in the Nationals' organization came down with some sort of injury.
The 33-year-old Maldonado appeared in four games, going 0-for-9 with one RBI and two walks before landing on the disabled list with a back injury.
He played 51 games at Syracuse, batting .210.
Maldonado was behind Sandy Leon and Jhonatan Solano - two young, fairly highly regarded prospects - on the organizational depth chart at catcher.
Baseball America's Matt Eddy first reported the news on Carroll and Maldonado.